From 308d9fade64b5cd1292f4dceb053cc5ab7a322de Mon Sep 17 00:00:00 2001 From: Tad Date: Tue, 26 May 2015 14:05:46 -0400 Subject: [PATCH] Missing files --- Documentation/lzo.txt | 164 ++ arch/x86/include/asm/espfix.h | 16 + arch/x86/kernel/espfix_64.c | 208 ++ block/bfq-cgroup.c | 908 +++++++++ block/bfq-ioc.c | 36 + block/bfq-iosched.c | 4208 +++++++++++++++++++++++++++++++++++++++++ block/bfq-sched.c | 1186 ++++++++++++ block/bfq.h | 809 ++++++++ block/fiops-iosched.c | 753 ++++++++ block/sio-iosched.c | 403 ++++ block/sioplus-iosched.c | 405 ++++ block/tripndroid-iosched.c | 261 +++ block/vr-iosched.c | 432 +++++ block/zen-iosched.c | 277 +++ drivers/md/dm-builtin.c | 50 + 15 files changed, 10116 insertions(+) create mode 100644 Documentation/lzo.txt create mode 100644 arch/x86/include/asm/espfix.h create mode 100644 arch/x86/kernel/espfix_64.c create mode 100644 block/bfq-cgroup.c create mode 100644 block/bfq-ioc.c create mode 100644 block/bfq-iosched.c create mode 100644 block/bfq-sched.c create mode 100644 block/bfq.h create mode 100644 block/fiops-iosched.c create mode 100644 block/sio-iosched.c create mode 100644 block/sioplus-iosched.c create mode 100644 block/tripndroid-iosched.c create mode 100644 block/vr-iosched.c create mode 100644 block/zen-iosched.c create mode 100644 drivers/md/dm-builtin.c diff --git a/Documentation/lzo.txt b/Documentation/lzo.txt new file mode 100644 index 0000000..ea45dd3 --- /dev/null +++ b/Documentation/lzo.txt @@ -0,0 +1,164 @@ + +LZO stream format as understood by Linux's LZO decompressor +=========================================================== + +Introduction + + This is not a specification. No specification seems to be publicly available + for the LZO stream format. This document describes what input format the LZO + decompressor as implemented in the Linux kernel understands. The file subject + of this analysis is lib/lzo/lzo1x_decompress_safe.c. No analysis was made on + the compressor nor on any other implementations though it seems likely that + the format matches the standard one. The purpose of this document is to + better understand what the code does in order to propose more efficient fixes + for future bug reports. + +Description + + The stream is composed of a series of instructions, operands, and data. The + instructions consist in a few bits representing an opcode, and bits forming + the operands for the instruction, whose size and position depend on the + opcode and on the number of literals copied by previous instruction. The + operands are used to indicate : + + - a distance when copying data from the dictionary (past output buffer) + - a length (number of bytes to copy from dictionary) + - the number of literals to copy, which is retained in variable "state" + as a piece of information for next instructions. + + Optionally depending on the opcode and operands, extra data may follow. These + extra data can be a complement for the operand (eg: a length or a distance + encoded on larger values), or a literal to be copied to the output buffer. + + The first byte of the block follows a different encoding from other bytes, it + seems to be optimized for literal use only, since there is no dictionary yet + prior to that byte. + + Lengths are always encoded on a variable size starting with a small number + of bits in the operand. If the number of bits isn't enough to represent the + length, up to 255 may be added in increments by consuming more bytes with a + rate of at most 255 per extra byte (thus the compression ratio cannot exceed + around 255:1). The variable length encoding using #bits is always the same : + + length = byte & ((1 << #bits) - 1) + if (!length) { + length = ((1 << #bits) - 1) + length += 255*(number of zero bytes) + length += first-non-zero-byte + } + length += constant (generally 2 or 3) + + For references to the dictionary, distances are relative to the output + pointer. Distances are encoded using very few bits belonging to certain + ranges, resulting in multiple copy instructions using different encodings. + Certain encodings involve one extra byte, others involve two extra bytes + forming a little-endian 16-bit quantity (marked LE16 below). + + After any instruction except the large literal copy, 0, 1, 2 or 3 literals + are copied before starting the next instruction. The number of literals that + were copied may change the meaning and behaviour of the next instruction. In + practice, only one instruction needs to know whether 0, less than 4, or more + literals were copied. This is the information stored in the variable + in this implementation. This number of immediate literals to be copied is + generally encoded in the last two bits of the instruction but may also be + taken from the last two bits of an extra operand (eg: distance). + + End of stream is declared when a block copy of distance 0 is seen. Only one + instruction may encode this distance (0001HLLL), it takes one LE16 operand + for the distance, thus requiring 3 bytes. + + IMPORTANT NOTE : in the code some length checks are missing because certain + instructions are called under the assumption that a certain number of bytes + follow because it has already been garanteed before parsing the instructions. + They just have to "refill" this credit if they consume extra bytes. This is + an implementation design choice independant on the algorithm or encoding. + +Byte sequences + + First byte encoding : + + 0..17 : follow regular instruction encoding, see below. It is worth + noting that codes 16 and 17 will represent a block copy from + the dictionary which is empty, and that they will always be + invalid at this place. + + 18..21 : copy 0..3 literals + state = (byte - 17) = 0..3 [ copy literals ] + skip byte + + 22..255 : copy literal string + length = (byte - 17) = 4..238 + state = 4 [ don't copy extra literals ] + skip byte + + Instruction encoding : + + 0 0 0 0 X X X X (0..15) + Depends on the number of literals copied by the last instruction. + If last instruction did not copy any literal (state == 0), this + encoding will be a copy of 4 or more literal, and must be interpreted + like this : + + 0 0 0 0 L L L L (0..15) : copy long literal string + length = 3 + (L ?: 15 + (zero_bytes * 255) + non_zero_byte) + state = 4 (no extra literals are copied) + + If last instruction used to copy between 1 to 3 literals (encoded in + the instruction's opcode or distance), the instruction is a copy of a + 2-byte block from the dictionary within a 1kB distance. It is worth + noting that this instruction provides little savings since it uses 2 + bytes to encode a copy of 2 other bytes but it encodes the number of + following literals for free. It must be interpreted like this : + + 0 0 0 0 D D S S (0..15) : copy 2 bytes from <= 1kB distance + length = 2 + state = S (copy S literals after this block) + Always followed by exactly one byte : H H H H H H H H + distance = (H << 2) + D + 1 + + If last instruction used to copy 4 or more literals (as detected by + state == 4), the instruction becomes a copy of a 3-byte block from the + dictionary from a 2..3kB distance, and must be interpreted like this : + + 0 0 0 0 D D S S (0..15) : copy 3 bytes from 2..3 kB distance + length = 3 + state = S (copy S literals after this block) + Always followed by exactly one byte : H H H H H H H H + distance = (H << 2) + D + 2049 + + 0 0 0 1 H L L L (16..31) + Copy of a block within 16..48kB distance (preferably less than 10B) + length = 2 + (L ?: 7 + (zero_bytes * 255) + non_zero_byte) + Always followed by exactly one LE16 : D D D D D D D D : D D D D D D S S + distance = 16384 + (H << 14) + D + state = S (copy S literals after this block) + End of stream is reached if distance == 16384 + + 0 0 1 L L L L L (32..63) + Copy of small block within 16kB distance (preferably less than 34B) + length = 2 + (L ?: 31 + (zero_bytes * 255) + non_zero_byte) + Always followed by exactly one LE16 : D D D D D D D D : D D D D D D S S + distance = D + 1 + state = S (copy S literals after this block) + + 0 1 L D D D S S (64..127) + Copy 3-4 bytes from block within 2kB distance + state = S (copy S literals after this block) + length = 3 + L + Always followed by exactly one byte : H H H H H H H H + distance = (H << 3) + D + 1 + + 1 L L D D D S S (128..255) + Copy 5-8 bytes from block within 2kB distance + state = S (copy S literals after this block) + length = 5 + L + Always followed by exactly one byte : H H H H H H H H + distance = (H << 3) + D + 1 + +Authors + + This document was written by Willy Tarreau on 2014/07/19 during an + analysis of the decompression code available in Linux 3.16-rc5. The code is + tricky, it is possible that this document contains mistakes or that a few + corner cases were overlooked. In any case, please report any doubt, fix, or + proposed updates to the author(s) so that the document can be updated. diff --git a/arch/x86/include/asm/espfix.h b/arch/x86/include/asm/espfix.h new file mode 100644 index 0000000..99efebb --- /dev/null +++ b/arch/x86/include/asm/espfix.h @@ -0,0 +1,16 @@ +#ifndef _ASM_X86_ESPFIX_H +#define _ASM_X86_ESPFIX_H + +#ifdef CONFIG_X86_64 + +#include + +DECLARE_PER_CPU_READ_MOSTLY(unsigned long, espfix_stack); +DECLARE_PER_CPU_READ_MOSTLY(unsigned long, espfix_waddr); + +extern void init_espfix_bsp(void); +extern void init_espfix_ap(void); + +#endif /* CONFIG_X86_64 */ + +#endif /* _ASM_X86_ESPFIX_H */ diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c new file mode 100644 index 0000000..94d857f --- /dev/null +++ b/arch/x86/kernel/espfix_64.c @@ -0,0 +1,208 @@ +/* ----------------------------------------------------------------------- * + * + * Copyright 2014 Intel Corporation; author: H. Peter Anvin + * + * This program is free software; you can redistribute it and/or modify it + * under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * This program is distributed in the hope it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * ----------------------------------------------------------------------- */ + +/* + * The IRET instruction, when returning to a 16-bit segment, only + * restores the bottom 16 bits of the user space stack pointer. This + * causes some 16-bit software to break, but it also leaks kernel state + * to user space. + * + * This works around this by creating percpu "ministacks", each of which + * is mapped 2^16 times 64K apart. When we detect that the return SS is + * on the LDT, we copy the IRET frame to the ministack and use the + * relevant alias to return to userspace. The ministacks are mapped + * readonly, so if the IRET fault we promote #GP to #DF which is an IST + * vector and thus has its own stack; we then do the fixup in the #DF + * handler. + * + * This file sets up the ministacks and the related page tables. The + * actual ministack invocation is in entry_64.S. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * Note: we only need 6*8 = 48 bytes for the espfix stack, but round + * it up to a cache line to avoid unnecessary sharing. + */ +#define ESPFIX_STACK_SIZE (8*8UL) +#define ESPFIX_STACKS_PER_PAGE (PAGE_SIZE/ESPFIX_STACK_SIZE) + +/* There is address space for how many espfix pages? */ +#define ESPFIX_PAGE_SPACE (1UL << (PGDIR_SHIFT-PAGE_SHIFT-16)) + +#define ESPFIX_MAX_CPUS (ESPFIX_STACKS_PER_PAGE * ESPFIX_PAGE_SPACE) +#if CONFIG_NR_CPUS > ESPFIX_MAX_CPUS +# error "Need more than one PGD for the ESPFIX hack" +#endif + +#define PGALLOC_GFP (GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO) + +/* This contains the *bottom* address of the espfix stack */ +DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_stack); +DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_waddr); + +/* Initialization mutex - should this be a spinlock? */ +static DEFINE_MUTEX(espfix_init_mutex); + +/* Page allocation bitmap - each page serves ESPFIX_STACKS_PER_PAGE CPUs */ +#define ESPFIX_MAX_PAGES DIV_ROUND_UP(CONFIG_NR_CPUS, ESPFIX_STACKS_PER_PAGE) +static void *espfix_pages[ESPFIX_MAX_PAGES]; + +static __page_aligned_bss pud_t espfix_pud_page[PTRS_PER_PUD] + __aligned(PAGE_SIZE); + +static unsigned int page_random, slot_random; + +/* + * This returns the bottom address of the espfix stack for a specific CPU. + * The math allows for a non-power-of-two ESPFIX_STACK_SIZE, in which case + * we have to account for some amount of padding at the end of each page. + */ +static inline unsigned long espfix_base_addr(unsigned int cpu) +{ + unsigned long page, slot; + unsigned long addr; + + page = (cpu / ESPFIX_STACKS_PER_PAGE) ^ page_random; + slot = (cpu + slot_random) % ESPFIX_STACKS_PER_PAGE; + addr = (page << PAGE_SHIFT) + (slot * ESPFIX_STACK_SIZE); + addr = (addr & 0xffffUL) | ((addr & ~0xffffUL) << 16); + addr += ESPFIX_BASE_ADDR; + return addr; +} + +#define PTE_STRIDE (65536/PAGE_SIZE) +#define ESPFIX_PTE_CLONES (PTRS_PER_PTE/PTE_STRIDE) +#define ESPFIX_PMD_CLONES PTRS_PER_PMD +#define ESPFIX_PUD_CLONES (65536/(ESPFIX_PTE_CLONES*ESPFIX_PMD_CLONES)) + +#define PGTABLE_PROT ((_KERNPG_TABLE & ~_PAGE_RW) | _PAGE_NX) + +static void init_espfix_random(void) +{ + unsigned long rand; + + /* + * This is run before the entropy pools are initialized, + * but this is hopefully better than nothing. + */ + if (!arch_get_random_long(&rand)) { + /* The constant is an arbitrary large prime */ + rdtscll(rand); + rand *= 0xc345c6b72fd16123UL; + } + + slot_random = rand % ESPFIX_STACKS_PER_PAGE; + page_random = (rand / ESPFIX_STACKS_PER_PAGE) + & (ESPFIX_PAGE_SPACE - 1); +} + +void __init init_espfix_bsp(void) +{ + pgd_t *pgd_p; + pteval_t ptemask; + + ptemask = __supported_pte_mask; + + /* Install the espfix pud into the kernel page directory */ + pgd_p = &init_level4_pgt[pgd_index(ESPFIX_BASE_ADDR)]; + pgd_populate(&init_mm, pgd_p, (pud_t *)espfix_pud_page); + + /* Randomize the locations */ + init_espfix_random(); + + /* The rest is the same as for any other processor */ + init_espfix_ap(); +} + +void init_espfix_ap(void) +{ + unsigned int cpu, page; + unsigned long addr; + pud_t pud, *pud_p; + pmd_t pmd, *pmd_p; + pte_t pte, *pte_p; + int n; + void *stack_page; + pteval_t ptemask; + + /* We only have to do this once... */ + if (likely(this_cpu_read(espfix_stack))) + return; /* Already initialized */ + + cpu = smp_processor_id(); + addr = espfix_base_addr(cpu); + page = cpu/ESPFIX_STACKS_PER_PAGE; + + /* Did another CPU already set this up? */ + stack_page = ACCESS_ONCE(espfix_pages[page]); + if (likely(stack_page)) + goto done; + + mutex_lock(&espfix_init_mutex); + + /* Did we race on the lock? */ + stack_page = ACCESS_ONCE(espfix_pages[page]); + if (stack_page) + goto unlock_done; + + ptemask = __supported_pte_mask; + + pud_p = &espfix_pud_page[pud_index(addr)]; + pud = *pud_p; + if (!pud_present(pud)) { + pmd_p = (pmd_t *)__get_free_page(PGALLOC_GFP); + pud = __pud(__pa(pmd_p) | (PGTABLE_PROT & ptemask)); + paravirt_alloc_pmd(&init_mm, __pa(pmd_p) >> PAGE_SHIFT); + for (n = 0; n < ESPFIX_PUD_CLONES; n++) + set_pud(&pud_p[n], pud); + } + + pmd_p = pmd_offset(&pud, addr); + pmd = *pmd_p; + if (!pmd_present(pmd)) { + pte_p = (pte_t *)__get_free_page(PGALLOC_GFP); + pmd = __pmd(__pa(pte_p) | (PGTABLE_PROT & ptemask)); + paravirt_alloc_pte(&init_mm, __pa(pte_p) >> PAGE_SHIFT); + for (n = 0; n < ESPFIX_PMD_CLONES; n++) + set_pmd(&pmd_p[n], pmd); + } + + pte_p = pte_offset_kernel(&pmd, addr); + stack_page = (void *)__get_free_page(GFP_KERNEL); + pte = __pte(__pa(stack_page) | (__PAGE_KERNEL_RO & ptemask)); + for (n = 0; n < ESPFIX_PTE_CLONES; n++) + set_pte(&pte_p[n*PTE_STRIDE], pte); + + /* Job is done for this CPU and any CPU which shares this page */ + ACCESS_ONCE(espfix_pages[page]) = stack_page; + +unlock_done: + mutex_unlock(&espfix_init_mutex); +done: + this_cpu_write(espfix_stack, addr); + this_cpu_write(espfix_waddr, (unsigned long)stack_page + + (addr & ~PAGE_MASK)); +} diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c new file mode 100644 index 0000000..8399c92 --- /dev/null +++ b/block/bfq-cgroup.c @@ -0,0 +1,908 @@ +/* + * BFQ: CGROUPS support. + * + * Based on ideas and code from CFQ: + * Copyright (C) 2003 Jens Axboe + * + * Copyright (C) 2008 Fabio Checconi + * Paolo Valente + * + * Copyright (C) 2010 Paolo Valente + * + * Licensed under the GPL-2 as detailed in the accompanying COPYING.BFQ + * file. + */ + +#ifdef CONFIG_CGROUP_BFQIO +static struct bfqio_cgroup bfqio_root_cgroup = { + .weight = BFQ_DEFAULT_GRP_WEIGHT, + .ioprio = BFQ_DEFAULT_GRP_IOPRIO, + .ioprio_class = BFQ_DEFAULT_GRP_CLASS, +}; + +static inline void bfq_init_entity(struct bfq_entity *entity, + struct bfq_group *bfqg) +{ + entity->weight = entity->new_weight; + entity->orig_weight = entity->new_weight; + entity->ioprio = entity->new_ioprio; + entity->ioprio_class = entity->new_ioprio_class; + entity->parent = bfqg->my_entity; + entity->sched_data = &bfqg->sched_data; +} + +static struct bfqio_cgroup *cgroup_to_bfqio(struct cgroup *cgroup) +{ + return container_of(cgroup_subsys_state(cgroup, bfqio_subsys_id), + struct bfqio_cgroup, css); +} + +/* + * Search the bfq_group for bfqd into the hash table (by now only a list) + * of bgrp. Must be called under rcu_read_lock(). + */ +static struct bfq_group *bfqio_lookup_group(struct bfqio_cgroup *bgrp, + struct bfq_data *bfqd) +{ + struct bfq_group *bfqg; + struct hlist_node *n; + void *key; + + hlist_for_each_entry_rcu(bfqg, n, &bgrp->group_data, group_node) { + key = rcu_dereference(bfqg->bfqd); + if (key == bfqd) + return bfqg; + } + + return NULL; +} + +static inline void bfq_group_init_entity(struct bfqio_cgroup *bgrp, + struct bfq_group *bfqg) +{ + struct bfq_entity *entity = &bfqg->entity; + + /* + * If the weight of the entity has never been set via the sysfs + * interface, then bgrp->weight == 0. In this case we initialize + * the weight from the current ioprio value. Otherwise, the group + * weight, if set, has priority over the ioprio value. + */ + if (bgrp->weight == 0) { + entity->new_weight = bfq_ioprio_to_weight(bgrp->ioprio); + entity->new_ioprio = bgrp->ioprio; + } else { + if (bgrp->weight < BFQ_MIN_WEIGHT || + bgrp->weight > BFQ_MAX_WEIGHT) { + printk(KERN_CRIT "bfq_group_init_entity: " + "bgrp->weight %d\n", bgrp->weight); + BUG(); + } + entity->new_weight = bgrp->weight; + entity->new_ioprio = bfq_weight_to_ioprio(bgrp->weight); + } + entity->orig_weight = entity->weight = entity->new_weight; + entity->ioprio = entity->new_ioprio; + entity->ioprio_class = entity->new_ioprio_class = bgrp->ioprio_class; + entity->my_sched_data = &bfqg->sched_data; + bfqg->active_entities = 0; +} + +static inline void bfq_group_set_parent(struct bfq_group *bfqg, + struct bfq_group *parent) +{ + struct bfq_entity *entity; + + BUG_ON(parent == NULL); + BUG_ON(bfqg == NULL); + + entity = &bfqg->entity; + entity->parent = parent->my_entity; + entity->sched_data = &parent->sched_data; +} + +/** + * bfq_group_chain_alloc - allocate a chain of groups. + * @bfqd: queue descriptor. + * @cgroup: the leaf cgroup this chain starts from. + * + * Allocate a chain of groups starting from the one belonging to + * @cgroup up to the root cgroup. Stop if a cgroup on the chain + * to the root has already an allocated group on @bfqd. + */ +static struct bfq_group *bfq_group_chain_alloc(struct bfq_data *bfqd, + struct cgroup *cgroup) +{ + struct bfqio_cgroup *bgrp; + struct bfq_group *bfqg, *prev = NULL, *leaf = NULL; + + for (; cgroup != NULL; cgroup = cgroup->parent) { + bgrp = cgroup_to_bfqio(cgroup); + + bfqg = bfqio_lookup_group(bgrp, bfqd); + if (bfqg != NULL) { + /* + * All the cgroups in the path from there to the + * root must have a bfq_group for bfqd, so we don't + * need any more allocations. + */ + break; + } + + bfqg = kzalloc(sizeof(*bfqg), GFP_ATOMIC); + if (bfqg == NULL) + goto cleanup; + + bfq_group_init_entity(bgrp, bfqg); + bfqg->my_entity = &bfqg->entity; + + if (leaf == NULL) { + leaf = bfqg; + prev = leaf; + } else { + bfq_group_set_parent(prev, bfqg); + /* + * Build a list of allocated nodes using the bfqd + * filed, that is still unused and will be + * initialized only after the node will be + * connected. + */ + prev->bfqd = bfqg; + prev = bfqg; + } + } + + return leaf; + +cleanup: + while (leaf != NULL) { + prev = leaf; + leaf = leaf->bfqd; + kfree(prev); + } + + return NULL; +} + +/** + * bfq_group_chain_link - link an allocated group chain to a cgroup + * hierarchy. + * @bfqd: the queue descriptor. + * @cgroup: the leaf cgroup to start from. + * @leaf: the leaf group (to be associated to @cgroup). + * + * Try to link a chain of groups to a cgroup hierarchy, connecting the + * nodes bottom-up, so we can be sure that when we find a cgroup in the + * hierarchy that already as a group associated to @bfqd all the nodes + * in the path to the root cgroup have one too. + * + * On locking: the queue lock protects the hierarchy (there is a hierarchy + * per device) while the bfqio_cgroup lock protects the list of groups + * belonging to the same cgroup. + */ +static void bfq_group_chain_link(struct bfq_data *bfqd, struct cgroup *cgroup, + struct bfq_group *leaf) +{ + struct bfqio_cgroup *bgrp; + struct bfq_group *bfqg, *next, *prev = NULL; + unsigned long flags; + + assert_spin_locked(bfqd->queue->queue_lock); + + for (; cgroup != NULL && leaf != NULL; cgroup = cgroup->parent) { + bgrp = cgroup_to_bfqio(cgroup); + next = leaf->bfqd; + + bfqg = bfqio_lookup_group(bgrp, bfqd); + BUG_ON(bfqg != NULL); + + spin_lock_irqsave(&bgrp->lock, flags); + + rcu_assign_pointer(leaf->bfqd, bfqd); + hlist_add_head_rcu(&leaf->group_node, &bgrp->group_data); + hlist_add_head(&leaf->bfqd_node, &bfqd->group_list); + + spin_unlock_irqrestore(&bgrp->lock, flags); + + prev = leaf; + leaf = next; + } + + BUG_ON(cgroup == NULL && leaf != NULL); + if (cgroup != NULL && prev != NULL) { + bgrp = cgroup_to_bfqio(cgroup); + bfqg = bfqio_lookup_group(bgrp, bfqd); + bfq_group_set_parent(prev, bfqg); + } +} + +/** + * bfq_find_alloc_group - return the group associated to @bfqd in @cgroup. + * @bfqd: queue descriptor. + * @cgroup: cgroup being searched for. + * + * Return a group associated to @bfqd in @cgroup, allocating one if + * necessary. When a group is returned all the cgroups in the path + * to the root have a group associated to @bfqd. + * + * If the allocation fails, return the root group: this breaks guarantees + * but is a safe fallback. If this loss becomes a problem it can be + * mitigated using the equivalent weight (given by the product of the + * weights of the groups in the path from @group to the root) in the + * root scheduler. + * + * We allocate all the missing nodes in the path from the leaf cgroup + * to the root and we connect the nodes only after all the allocations + * have been successful. + */ +static struct bfq_group *bfq_find_alloc_group(struct bfq_data *bfqd, + struct cgroup *cgroup) +{ + struct bfqio_cgroup *bgrp = cgroup_to_bfqio(cgroup); + struct bfq_group *bfqg; + + bfqg = bfqio_lookup_group(bgrp, bfqd); + if (bfqg != NULL) + return bfqg; + + bfqg = bfq_group_chain_alloc(bfqd, cgroup); + if (bfqg != NULL) + bfq_group_chain_link(bfqd, cgroup, bfqg); + else + bfqg = bfqd->root_group; + + return bfqg; +} + +/** + * bfq_bfqq_move - migrate @bfqq to @bfqg. + * @bfqd: queue descriptor. + * @bfqq: the queue to move. + * @entity: @bfqq's entity. + * @bfqg: the group to move to. + * + * Move @bfqq to @bfqg, deactivating it from its old group and reactivating + * it on the new one. Avoid putting the entity on the old group idle tree. + * + * Must be called under the queue lock; the cgroup owning @bfqg must + * not disappear (by now this just means that we are called under + * rcu_read_lock()). + */ +static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq, + struct bfq_entity *entity, struct bfq_group *bfqg) +{ + int busy, resume; + + busy = bfq_bfqq_busy(bfqq); + resume = !RB_EMPTY_ROOT(&bfqq->sort_list); + + BUG_ON(resume && !entity->on_st); + BUG_ON(busy && !resume && entity->on_st && + bfqq != bfqd->in_service_queue); + + if (busy) { + BUG_ON(atomic_read(&bfqq->ref) < 2); + + if (!resume) + bfq_del_bfqq_busy(bfqd, bfqq, 0); + else + bfq_deactivate_bfqq(bfqd, bfqq, 0); + } else if (entity->on_st) + bfq_put_idle_entity(bfq_entity_service_tree(entity), entity); + + /* + * Here we use a reference to bfqg. We don't need a refcounter + * as the cgroup reference will not be dropped, so that its + * destroy() callback will not be invoked. + */ + entity->parent = bfqg->my_entity; + entity->sched_data = &bfqg->sched_data; + + if (busy && resume) + bfq_activate_bfqq(bfqd, bfqq); + + if (bfqd->in_service_queue == NULL && !bfqd->rq_in_driver) + bfq_schedule_dispatch(bfqd); +} + +/** + * __bfq_bic_change_cgroup - move @bic to @cgroup. + * @bfqd: the queue descriptor. + * @bic: the bic to move. + * @cgroup: the cgroup to move to. + * + * Move bic to cgroup, assuming that bfqd->queue is locked; the caller + * has to make sure that the reference to cgroup is valid across the call. + * + * NOTE: an alternative approach might have been to store the current + * cgroup in bfqq and getting a reference to it, reducing the lookup + * time here, at the price of slightly more complex code. + */ +static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd, + struct bfq_io_cq *bic, + struct cgroup *cgroup) +{ + struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0); + struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1); + struct bfq_entity *entity; + struct bfq_group *bfqg; + struct bfqio_cgroup *bgrp; + + bgrp = cgroup_to_bfqio(cgroup); + + bfqg = bfq_find_alloc_group(bfqd, cgroup); + if (async_bfqq != NULL) { + entity = &async_bfqq->entity; + + if (entity->sched_data != &bfqg->sched_data) { + bic_set_bfqq(bic, NULL, 0); + bfq_log_bfqq(bfqd, async_bfqq, + "bic_change_group: %p %d", + async_bfqq, atomic_read(&async_bfqq->ref)); + bfq_put_queue(async_bfqq); + } + } + + if (sync_bfqq != NULL) { + entity = &sync_bfqq->entity; + if (entity->sched_data != &bfqg->sched_data) + bfq_bfqq_move(bfqd, sync_bfqq, entity, bfqg); + } + + return bfqg; +} + +/** + * bfq_bic_change_cgroup - move @bic to @cgroup. + * @bic: the bic being migrated. + * @cgroup: the destination cgroup. + * + * When the task owning @bic is moved to @cgroup, @bic is immediately + * moved into its new parent group. + */ +static void bfq_bic_change_cgroup(struct bfq_io_cq *bic, + struct cgroup *cgroup) +{ + struct bfq_data *bfqd; + unsigned long uninitialized_var(flags); + + bfqd = bfq_get_bfqd_locked(&(bic->icq.q->elevator->elevator_data), + &flags); + if (bfqd != NULL) { + __bfq_bic_change_cgroup(bfqd, bic, cgroup); + bfq_put_bfqd_unlock(bfqd, &flags); + } +} + +/** + * bfq_bic_update_cgroup - update the cgroup of @bic. + * @bic: the @bic to update. + * + * Make sure that @bic is enqueued in the cgroup of the current task. + * We need this in addition to moving bics during the cgroup attach + * phase because the task owning @bic could be at its first disk + * access or we may end up in the root cgroup as the result of a + * memory allocation failure and here we try to move to the right + * group. + * + * Must be called under the queue lock. It is safe to use the returned + * value even after the rcu_read_unlock() as the migration/destruction + * paths act under the queue lock too. IOW it is impossible to race with + * group migration/destruction and end up with an invalid group as: + * a) here cgroup has not yet been destroyed, nor its destroy callback + * has started execution, as current holds a reference to it, + * b) if it is destroyed after rcu_read_unlock() [after current is + * migrated to a different cgroup] its attach() callback will have + * taken care of remove all the references to the old cgroup data. + */ +static struct bfq_group *bfq_bic_update_cgroup(struct bfq_io_cq *bic) +{ + struct bfq_data *bfqd = bic_to_bfqd(bic); + struct bfq_group *bfqg; + struct cgroup *cgroup; + + BUG_ON(bfqd == NULL); + + rcu_read_lock(); + cgroup = task_cgroup(current, bfqio_subsys_id); + bfqg = __bfq_bic_change_cgroup(bfqd, bic, cgroup); + rcu_read_unlock(); + + return bfqg; +} + +/** + * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st. + * @st: the service tree being flushed. + */ +static inline void bfq_flush_idle_tree(struct bfq_service_tree *st) +{ + struct bfq_entity *entity = st->first_idle; + + for (; entity != NULL; entity = st->first_idle) + __bfq_deactivate_entity(entity, 0); +} + +/** + * bfq_reparent_leaf_entity - move leaf entity to the root_group. + * @bfqd: the device data structure with the root group. + * @entity: the entity to move. + */ +static inline void bfq_reparent_leaf_entity(struct bfq_data *bfqd, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + + BUG_ON(bfqq == NULL); + bfq_bfqq_move(bfqd, bfqq, entity, bfqd->root_group); + return; +} + +/** + * bfq_reparent_active_entities - move to the root group all active + * entities. + * @bfqd: the device data structure with the root group. + * @bfqg: the group to move from. + * @st: the service tree with the entities. + * + * Needs queue_lock to be taken and reference to be valid over the call. + */ +static inline void bfq_reparent_active_entities(struct bfq_data *bfqd, + struct bfq_group *bfqg, + struct bfq_service_tree *st) +{ + struct rb_root *active = &st->active; + struct bfq_entity *entity = NULL; + + if (!RB_EMPTY_ROOT(&st->active)) + entity = bfq_entity_of(rb_first(active)); + + for (; entity != NULL; entity = bfq_entity_of(rb_first(active))) + bfq_reparent_leaf_entity(bfqd, entity); + + if (bfqg->sched_data.in_service_entity != NULL) + bfq_reparent_leaf_entity(bfqd, + bfqg->sched_data.in_service_entity); + + return; +} + +/** + * bfq_destroy_group - destroy @bfqg. + * @bgrp: the bfqio_cgroup containing @bfqg. + * @bfqg: the group being destroyed. + * + * Destroy @bfqg, making sure that it is not referenced from its parent. + */ +static void bfq_destroy_group(struct bfqio_cgroup *bgrp, struct bfq_group *bfqg) +{ + struct bfq_data *bfqd; + struct bfq_service_tree *st; + struct bfq_entity *entity = bfqg->my_entity; + unsigned long uninitialized_var(flags); + int i; + + hlist_del(&bfqg->group_node); + + /* + * Empty all service_trees belonging to this group before + * deactivating the group itself. + */ + for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) { + st = bfqg->sched_data.service_tree + i; + + /* + * The idle tree may still contain bfq_queues belonging + * to exited task because they never migrated to a different + * cgroup from the one being destroyed now. No one else + * can access them so it's safe to act without any lock. + */ + bfq_flush_idle_tree(st); + + /* + * It may happen that some queues are still active + * (busy) upon group destruction (if the corresponding + * processes have been forced to terminate). We move + * all the leaf entities corresponding to these queues + * to the root_group. + * Also, it may happen that the group has an entity + * in service, which is disconnected from the active + * tree: it must be moved, too. + * There is no need to put the sync queues, as the + * scheduler has taken no reference. + */ + bfqd = bfq_get_bfqd_locked(&bfqg->bfqd, &flags); + if (bfqd != NULL) { + bfq_reparent_active_entities(bfqd, bfqg, st); + bfq_put_bfqd_unlock(bfqd, &flags); + } + BUG_ON(!RB_EMPTY_ROOT(&st->active)); + BUG_ON(!RB_EMPTY_ROOT(&st->idle)); + } + BUG_ON(bfqg->sched_data.next_in_service != NULL); + BUG_ON(bfqg->sched_data.in_service_entity != NULL); + + /* + * We may race with device destruction, take extra care when + * dereferencing bfqg->bfqd. + */ + bfqd = bfq_get_bfqd_locked(&bfqg->bfqd, &flags); + if (bfqd != NULL) { + hlist_del(&bfqg->bfqd_node); + __bfq_deactivate_entity(entity, 0); + bfq_put_async_queues(bfqd, bfqg); + bfq_put_bfqd_unlock(bfqd, &flags); + } + BUG_ON(entity->tree != NULL); + + /* + * No need to defer the kfree() to the end of the RCU grace + * period: we are called from the destroy() callback of our + * cgroup, so we can be sure that no one is a) still using + * this cgroup or b) doing lookups in it. + */ + kfree(bfqg); +} + +static void bfq_end_wr_async(struct bfq_data *bfqd) +{ + struct hlist_node *pos, *n; + struct bfq_group *bfqg; + + hlist_for_each_entry_safe(bfqg, pos, n, &bfqd->group_list, bfqd_node) + bfq_end_wr_async_queues(bfqd, bfqg); + bfq_end_wr_async_queues(bfqd, bfqd->root_group); +} + +/** + * bfq_disconnect_groups - disconnect @bfqd from all its groups. + * @bfqd: the device descriptor being exited. + * + * When the device exits we just make sure that no lookup can return + * the now unused group structures. They will be deallocated on cgroup + * destruction. + */ +static void bfq_disconnect_groups(struct bfq_data *bfqd) +{ + struct hlist_node *pos, *n; + struct bfq_group *bfqg; + + bfq_log(bfqd, "disconnect_groups beginning"); + hlist_for_each_entry_safe(bfqg, pos, n, &bfqd->group_list, bfqd_node) { + hlist_del(&bfqg->bfqd_node); + + __bfq_deactivate_entity(bfqg->my_entity, 0); + + /* + * Don't remove from the group hash, just set an + * invalid key. No lookups can race with the + * assignment as bfqd is being destroyed; this + * implies also that new elements cannot be added + * to the list. + */ + rcu_assign_pointer(bfqg->bfqd, NULL); + + bfq_log(bfqd, "disconnect_groups: put async for group %p", + bfqg); + bfq_put_async_queues(bfqd, bfqg); + } +} + +static inline void bfq_free_root_group(struct bfq_data *bfqd) +{ + struct bfqio_cgroup *bgrp = &bfqio_root_cgroup; + struct bfq_group *bfqg = bfqd->root_group; + + bfq_put_async_queues(bfqd, bfqg); + + spin_lock_irq(&bgrp->lock); + hlist_del_rcu(&bfqg->group_node); + spin_unlock_irq(&bgrp->lock); + + /* + * No need to synchronize_rcu() here: since the device is gone + * there cannot be any read-side access to its root_group. + */ + kfree(bfqg); +} + +static struct bfq_group *bfq_alloc_root_group(struct bfq_data *bfqd, int node) +{ + struct bfq_group *bfqg; + struct bfqio_cgroup *bgrp; + int i; + + bfqg = kzalloc_node(sizeof(*bfqg), GFP_KERNEL, node); + if (bfqg == NULL) + return NULL; + + bfqg->entity.parent = NULL; + for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) + bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT; + + bgrp = &bfqio_root_cgroup; + spin_lock_irq(&bgrp->lock); + rcu_assign_pointer(bfqg->bfqd, bfqd); + hlist_add_head_rcu(&bfqg->group_node, &bgrp->group_data); + spin_unlock_irq(&bgrp->lock); + + return bfqg; +} + +#define SHOW_FUNCTION(__VAR) \ +static u64 bfqio_cgroup_##__VAR##_read(struct cgroup *cgroup, \ + struct cftype *cftype) \ +{ \ + struct bfqio_cgroup *bgrp; \ + u64 ret; \ + \ + if (!cgroup_lock_live_group(cgroup)) \ + return -ENODEV; \ + \ + bgrp = cgroup_to_bfqio(cgroup); \ + spin_lock_irq(&bgrp->lock); \ + ret = bgrp->__VAR; \ + spin_unlock_irq(&bgrp->lock); \ + \ + cgroup_unlock(); \ + \ + return ret; \ +} + +SHOW_FUNCTION(weight); +SHOW_FUNCTION(ioprio); +SHOW_FUNCTION(ioprio_class); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__VAR, __MIN, __MAX) \ +static int bfqio_cgroup_##__VAR##_write(struct cgroup *cgroup, \ + struct cftype *cftype, \ + u64 val) \ +{ \ + struct bfqio_cgroup *bgrp; \ + struct bfq_group *bfqg; \ + struct hlist_node *n; \ + \ + if (val < (__MIN) || val > (__MAX)) \ + return -EINVAL; \ + \ + if (!cgroup_lock_live_group(cgroup)) \ + return -ENODEV; \ + \ + bgrp = cgroup_to_bfqio(cgroup); \ + \ + spin_lock_irq(&bgrp->lock); \ + bgrp->__VAR = (unsigned short)val; \ + hlist_for_each_entry(bfqg, n, &bgrp->group_data, group_node) { \ + /* \ + * Setting the ioprio_changed flag of the entity \ + * to 1 with new_##__VAR == ##__VAR would re-set \ + * the value of the weight to its ioprio mapping. \ + * Set the flag only if necessary. \ + */ \ + if ((unsigned short)val != bfqg->entity.new_##__VAR) { \ + bfqg->entity.new_##__VAR = (unsigned short)val; \ + /* \ + * Make sure that the above new value has been \ + * stored in bfqg->entity.new_##__VAR before \ + * setting the ioprio_changed flag. In fact, \ + * this flag may be read asynchronously (in \ + * critical sections protected by a different \ + * lock than that held here), and finding this \ + * flag set may cause the execution of the code \ + * for updating parameters whose value may \ + * depend also on bfqg->entity.new_##__VAR (in \ + * __bfq_entity_update_weight_prio). \ + * This barrier makes sure that the new value \ + * of bfqg->entity.new_##__VAR is correctly \ + * seen in that code. \ + */ \ + smp_wmb(); \ + bfqg->entity.ioprio_changed = 1; \ + } \ + } \ + spin_unlock_irq(&bgrp->lock); \ + \ + cgroup_unlock(); \ + \ + return 0; \ +} + +STORE_FUNCTION(weight, BFQ_MIN_WEIGHT, BFQ_MAX_WEIGHT); +STORE_FUNCTION(ioprio, 0, IOPRIO_BE_NR - 1); +STORE_FUNCTION(ioprio_class, IOPRIO_CLASS_RT, IOPRIO_CLASS_IDLE); +#undef STORE_FUNCTION + +static struct cftype bfqio_files[] = { + { + .name = "weight", + .read_u64 = bfqio_cgroup_weight_read, + .write_u64 = bfqio_cgroup_weight_write, + }, + { + .name = "ioprio", + .read_u64 = bfqio_cgroup_ioprio_read, + .write_u64 = bfqio_cgroup_ioprio_write, + }, + { + .name = "ioprio_class", + .read_u64 = bfqio_cgroup_ioprio_class_read, + .write_u64 = bfqio_cgroup_ioprio_class_write, + }, +}; + +static int bfqio_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup) +{ + return cgroup_add_files(cgroup, subsys, bfqio_files, + ARRAY_SIZE(bfqio_files)); +} + +static struct cgroup_subsys_state *bfqio_create(struct cgroup *cgroup) +{ + struct bfqio_cgroup *bgrp; + + if (cgroup->parent != NULL) { + bgrp = kzalloc(sizeof(*bgrp), GFP_KERNEL); + if (bgrp == NULL) + return ERR_PTR(-ENOMEM); + } else + bgrp = &bfqio_root_cgroup; + + spin_lock_init(&bgrp->lock); + INIT_HLIST_HEAD(&bgrp->group_data); + bgrp->ioprio = BFQ_DEFAULT_GRP_IOPRIO; + bgrp->ioprio_class = BFQ_DEFAULT_GRP_CLASS; + + return &bgrp->css; +} + +/* + * We cannot support shared io contexts, as we have no means to support + * two tasks with the same ioc in two different groups without major rework + * of the main bic/bfqq data structures. By now we allow a task to change + * its cgroup only if it's the only owner of its ioc; the drawback of this + * behavior is that a group containing a task that forked using CLONE_IO + * will not be destroyed until the tasks sharing the ioc die. + */ +static int bfqio_can_attach(struct cgroup *cgroup, struct cgroup_taskset *tset) +{ + struct task_struct *task; + struct io_context *ioc; + int ret = 0; + + cgroup_taskset_for_each(task, cgroup, tset) { + /* task_lock() is needed to avoid races with exit_io_context() */ + task_lock(task); + ioc = task->io_context; + if (ioc != NULL && atomic_read(&ioc->nr_tasks) > 1) + /* + * ioc == NULL means that the task is either too + * young or exiting: if it has still no ioc the + * ioc can't be shared, if the task is exiting the + * attach will fail anyway, no matter what we + * return here. + */ + ret = -EINVAL; + task_unlock(task); + if (ret) + break; + } + + return ret; +} + +static void bfqio_attach(struct cgroup *cgroup, struct cgroup_taskset *tset) +{ + struct task_struct *task; + struct io_context *ioc; + struct io_cq *icq; + struct hlist_node *n; + + /* + * IMPORTANT NOTE: The move of more than one process at a time to a + * new group has not yet been tested. + */ + cgroup_taskset_for_each(task, cgroup, tset) { + ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE); + if (ioc) { + /* + * Handle cgroup change here. + */ + rcu_read_lock(); + hlist_for_each_entry_rcu(icq, n, &ioc->icq_list, ioc_node) + if (!strncmp( + icq->q->elevator->type->elevator_name, + "bfq", ELV_NAME_MAX)) + bfq_bic_change_cgroup(icq_to_bic(icq), + cgroup); + rcu_read_unlock(); + put_io_context(ioc); + } + } +} + +static void bfqio_destroy(struct cgroup *cgroup) +{ + struct bfqio_cgroup *bgrp = cgroup_to_bfqio(cgroup); + struct hlist_node *n, *tmp; + struct bfq_group *bfqg; + + /* + * Since we are destroying the cgroup, there are no more tasks + * referencing it, and all the RCU grace periods that may have + * referenced it are ended (as the destruction of the parent + * cgroup is RCU-safe); bgrp->group_data will not be accessed by + * anything else and we don't need any synchronization. + */ + hlist_for_each_entry_safe(bfqg, n, tmp, &bgrp->group_data, group_node) + bfq_destroy_group(bgrp, bfqg); + + BUG_ON(!hlist_empty(&bgrp->group_data)); + + kfree(bgrp); +} + +struct cgroup_subsys bfqio_subsys = { + .name = "bfqio", + .create = bfqio_create, + .can_attach = bfqio_can_attach, + .attach = bfqio_attach, + .destroy = bfqio_destroy, + .populate = bfqio_populate, + .subsys_id = bfqio_subsys_id, +}; +#else +static inline void bfq_init_entity(struct bfq_entity *entity, + struct bfq_group *bfqg) +{ + entity->weight = entity->new_weight; + entity->orig_weight = entity->new_weight; + entity->ioprio = entity->new_ioprio; + entity->ioprio_class = entity->new_ioprio_class; + entity->sched_data = &bfqg->sched_data; +} + +static inline struct bfq_group * +bfq_bic_update_cgroup(struct bfq_io_cq *bic) +{ + struct bfq_data *bfqd = bic_to_bfqd(bic); + return bfqd->root_group; +} + +static inline void bfq_bfqq_move(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + struct bfq_entity *entity, + struct bfq_group *bfqg) +{ +} + +static void bfq_end_wr_async(struct bfq_data *bfqd) +{ + bfq_end_wr_async_queues(bfqd, bfqd->root_group); +} + +static inline void bfq_disconnect_groups(struct bfq_data *bfqd) +{ + bfq_put_async_queues(bfqd, bfqd->root_group); +} + +static inline void bfq_free_root_group(struct bfq_data *bfqd) +{ + kfree(bfqd->root_group); +} + +static struct bfq_group *bfq_alloc_root_group(struct bfq_data *bfqd, int node) +{ + struct bfq_group *bfqg; + int i; + + bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node); + if (bfqg == NULL) + return NULL; + + for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) + bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT; + + return bfqg; +} +#endif diff --git a/block/bfq-ioc.c b/block/bfq-ioc.c new file mode 100644 index 0000000..7f6b000 --- /dev/null +++ b/block/bfq-ioc.c @@ -0,0 +1,36 @@ +/* + * BFQ: I/O context handling. + * + * Based on ideas and code from CFQ: + * Copyright (C) 2003 Jens Axboe + * + * Copyright (C) 2008 Fabio Checconi + * Paolo Valente + * + * Copyright (C) 2010 Paolo Valente + */ + +/** + * icq_to_bic - convert iocontext queue structure to bfq_io_cq. + * @icq: the iocontext queue. + */ +static inline struct bfq_io_cq *icq_to_bic(struct io_cq *icq) +{ + /* bic->icq is the first member, %NULL will convert to %NULL */ + return container_of(icq, struct bfq_io_cq, icq); +} + +/** + * bfq_bic_lookup - search into @ioc a bic associated to @bfqd. + * @bfqd: the lookup key. + * @ioc: the io_context of the process doing I/O. + * + * Queue lock must be held. + */ +static inline struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd, + struct io_context *ioc) +{ + if (ioc) + return icq_to_bic(ioc_lookup_icq(ioc, bfqd->queue)); + return NULL; +} diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c new file mode 100644 index 0000000..152992b --- /dev/null +++ b/block/bfq-iosched.c @@ -0,0 +1,4208 @@ +/* + * Budget Fair Queueing (BFQ) disk scheduler. + * + * Based on ideas and code from CFQ: + * Copyright (C) 2003 Jens Axboe + * + * Copyright (C) 2008 Fabio Checconi + * Paolo Valente + * + * Copyright (C) 2010 Paolo Valente + * + * Licensed under the GPL-2 as detailed in the accompanying COPYING.BFQ + * file. + * + * BFQ is a proportional-share storage-I/O scheduling algorithm based on + * the slice-by-slice service scheme of CFQ. But BFQ assigns budgets, + * measured in number of sectors, to processes instead of time slices. The + * device is not granted to the in-service process for a given time slice, + * but until it has exhausted its assigned budget. This change from the time + * to the service domain allows BFQ to distribute the device throughput + * among processes as desired, without any distortion due to ZBR, workload + * fluctuations or other factors. BFQ uses an ad hoc internal scheduler, + * called B-WF2Q+, to schedule processes according to their budgets. More + * precisely, BFQ schedules queues associated to processes. Thanks to the + * accurate policy of B-WF2Q+, BFQ can afford to assign high budgets to + * I/O-bound processes issuing sequential requests (to boost the + * throughput), and yet guarantee a low latency to interactive and soft + * real-time applications. + * + * BFQ is described in [1], where also a reference to the initial, more + * theoretical paper on BFQ can be found. The interested reader can find + * in the latter paper full details on the main algorithm, as well as + * formulas of the guarantees and formal proofs of all the properties. + * With respect to the version of BFQ presented in these papers, this + * implementation adds a few more heuristics, such as the one that + * guarantees a low latency to soft real-time applications, and a + * hierarchical extension based on H-WF2Q+. + * + * B-WF2Q+ is based on WF2Q+, that is described in [2], together with + * H-WF2Q+, while the augmented tree used to implement B-WF2Q+ with O(log N) + * complexity derives from the one introduced with EEVDF in [3]. + * + * [1] P. Valente and M. Andreolini, ``Improving Application Responsiveness + * with the BFQ Disk I/O Scheduler'', + * Proceedings of the 5th Annual International Systems and Storage + * Conference (SYSTOR '12), June 2012. + * + * http://algogroup.unimo.it/people/paolo/disk_sched/bf1-v1-suite-results.pdf + * + * [2] Jon C.R. Bennett and H. Zhang, ``Hierarchical Packet Fair Queueing + * Algorithms,'' IEEE/ACM Transactions on Networking, 5(5):675-689, + * Oct 1997. + * + * http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz + * + * [3] I. Stoica and H. Abdel-Wahab, ``Earliest Eligible Virtual Deadline + * First: A Flexible and Accurate Mechanism for Proportional Share + * Resource Allocation,'' technical report. + * + * http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include "bfq.h" +#include "blk.h" + +/* Max number of dispatches in one round of service. */ +static const int bfq_quantum = 4; + +/* Expiration time of sync (0) and async (1) requests, in jiffies. */ +static const int bfq_fifo_expire[2] = { HZ / 4, HZ / 8 }; + +/* Maximum backwards seek, in KiB. */ +static const int bfq_back_max = 16 * 1024; + +/* Penalty of a backwards seek, in number of sectors. */ +static const int bfq_back_penalty = 2; + +/* Idling period duration, in jiffies. */ +static int bfq_slice_idle = HZ / 125; + +/* Default maximum budget values, in sectors and number of requests. */ +static const int bfq_default_max_budget = 16 * 1024; +static const int bfq_max_budget_async_rq = 4; + +/* + * Async to sync throughput distribution is controlled as follows: + * when an async request is served, the entity is charged the number + * of sectors of the request, multiplied by the factor below + */ +static const int bfq_async_charge_factor = 10; + +/* Default timeout values, in jiffies, approximating CFQ defaults. */ +static const int bfq_timeout_sync = HZ / 8; +static int bfq_timeout_async = HZ / 25; + +struct kmem_cache *bfq_pool; + +/* Below this threshold (in ms), we consider thinktime immediate. */ +#define BFQ_MIN_TT 2 + +/* hw_tag detection: parallel requests threshold and min samples needed. */ +#define BFQ_HW_QUEUE_THRESHOLD 4 +#define BFQ_HW_QUEUE_SAMPLES 32 + +#define BFQQ_SEEK_THR (sector_t)(8 * 1024) +#define BFQQ_SEEKY(bfqq) ((bfqq)->seek_mean > BFQQ_SEEK_THR) + +/* Min samples used for peak rate estimation (for autotuning). */ +#define BFQ_PEAK_RATE_SAMPLES 32 + +/* Shift used for peak rate fixed precision calculations. */ +#define BFQ_RATE_SHIFT 16 + +/* + * By default, BFQ computes the duration of the weight raising for + * interactive applications automatically, using the following formula: + * duration = (R / r) * T, where r is the peak rate of the device, and + * R and T are two reference parameters. + * In particular, R is the peak rate of the reference device (see below), + * and T is a reference time: given the systems that are likely to be + * installed on the reference device according to its speed class, T is + * about the maximum time needed, under BFQ and while reading two files in + * parallel, to load typical large applications on these systems. + * In practice, the slower/faster the device at hand is, the more/less it + * takes to load applications with respect to the reference device. + * Accordingly, the longer/shorter BFQ grants weight raising to interactive + * applications. + * + * BFQ uses four different reference pairs (R, T), depending on: + * . whether the device is rotational or non-rotational; + * . whether the device is slow, such as old or portable HDDs, as well as + * SD cards, or fast, such as newer HDDs and SSDs. + * + * The device's speed class is dynamically (re)detected in + * bfq_update_peak_rate() every time the estimated peak rate is updated. + * + * In the following definitions, R_slow[0]/R_fast[0] and T_slow[0]/T_fast[0] + * are the reference values for a slow/fast rotational device, whereas + * R_slow[1]/R_fast[1] and T_slow[1]/T_fast[1] are the reference values for + * a slow/fast non-rotational device. Finally, device_speed_thresh are the + * thresholds used to switch between speed classes. + * Both the reference peak rates and the thresholds are measured in + * sectors/usec, left-shifted by BFQ_RATE_SHIFT. + */ +static int R_slow[2] = {1536, 10752}; +static int R_fast[2] = {17415, 34791}; +/* + * To improve readability, a conversion function is used to initialize the + * following arrays, which entails that they can be initialized only in a + * function. + */ +static int T_slow[2]; +static int T_fast[2]; +static int device_speed_thresh[2]; + +#define BFQ_SERVICE_TREE_INIT ((struct bfq_service_tree) \ + { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 }) + +#define RQ_BIC(rq) ((struct bfq_io_cq *) (rq)->elv.priv[0]) +#define RQ_BFQQ(rq) ((rq)->elv.priv[1]) + +static inline void bfq_schedule_dispatch(struct bfq_data *bfqd); + +#include "bfq-ioc.c" +#include "bfq-sched.c" +#include "bfq-cgroup.c" + +#define bfq_class_idle(bfqq) ((bfqq)->entity.ioprio_class ==\ + IOPRIO_CLASS_IDLE) +#define bfq_class_rt(bfqq) ((bfqq)->entity.ioprio_class ==\ + IOPRIO_CLASS_RT) + +#define bfq_sample_valid(samples) ((samples) > 80) + +/* + * We regard a request as SYNC, if either it's a read or has the SYNC bit + * set (in which case it could also be a direct WRITE). + */ +static inline int bfq_bio_sync(struct bio *bio) +{ + if (bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC)) + return 1; + + return 0; +} + +/* + * Scheduler run of queue, if there are requests pending and no one in the + * driver that will restart queueing. + */ +static inline void bfq_schedule_dispatch(struct bfq_data *bfqd) +{ + if (bfqd->queued != 0) { + bfq_log(bfqd, "schedule dispatch"); + kblockd_schedule_work(bfqd->queue, &bfqd->unplug_work); + } +} + +/* + * Lifted from AS - choose which of rq1 and rq2 that is best served now. + * We choose the request that is closesr to the head right now. Distance + * behind the head is penalized and only allowed to a certain extent. + */ +static struct request *bfq_choose_req(struct bfq_data *bfqd, + struct request *rq1, + struct request *rq2, + sector_t last) +{ + sector_t s1, s2, d1 = 0, d2 = 0; + unsigned long back_max; +#define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */ +#define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */ + unsigned wrap = 0; /* bit mask: requests behind the disk head? */ + + if (rq1 == NULL || rq1 == rq2) + return rq2; + if (rq2 == NULL) + return rq1; + + if (rq_is_sync(rq1) && !rq_is_sync(rq2)) + return rq1; + else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) + return rq2; + if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META)) + return rq1; + else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META)) + return rq2; + + s1 = blk_rq_pos(rq1); + s2 = blk_rq_pos(rq2); + + /* + * By definition, 1KiB is 2 sectors. + */ + back_max = bfqd->bfq_back_max * 2; + + /* + * Strict one way elevator _except_ in the case where we allow + * short backward seeks which are biased as twice the cost of a + * similar forward seek. + */ + if (s1 >= last) + d1 = s1 - last; + else if (s1 + back_max >= last) + d1 = (last - s1) * bfqd->bfq_back_penalty; + else + wrap |= BFQ_RQ1_WRAP; + + if (s2 >= last) + d2 = s2 - last; + else if (s2 + back_max >= last) + d2 = (last - s2) * bfqd->bfq_back_penalty; + else + wrap |= BFQ_RQ2_WRAP; + + /* Found required data */ + + /* + * By doing switch() on the bit mask "wrap" we avoid having to + * check two variables for all permutations: --> faster! + */ + switch (wrap) { + case 0: /* common case for CFQ: rq1 and rq2 not wrapped */ + if (d1 < d2) + return rq1; + else if (d2 < d1) + return rq2; + else { + if (s1 >= s2) + return rq1; + else + return rq2; + } + + case BFQ_RQ2_WRAP: + return rq1; + case BFQ_RQ1_WRAP: + return rq2; + case (BFQ_RQ1_WRAP|BFQ_RQ2_WRAP): /* both rqs wrapped */ + default: + /* + * Since both rqs are wrapped, + * start with the one that's further behind head + * (--> only *one* back seek required), + * since back seek takes more time than forward. + */ + if (s1 <= s2) + return rq1; + else + return rq2; + } +} + +static struct bfq_queue * +bfq_rq_pos_tree_lookup(struct bfq_data *bfqd, struct rb_root *root, + sector_t sector, struct rb_node **ret_parent, + struct rb_node ***rb_link) +{ + struct rb_node **p, *parent; + struct bfq_queue *bfqq = NULL; + + parent = NULL; + p = &root->rb_node; + while (*p) { + struct rb_node **n; + + parent = *p; + bfqq = rb_entry(parent, struct bfq_queue, pos_node); + + /* + * Sort strictly based on sector. Smallest to the left, + * largest to the right. + */ + if (sector > blk_rq_pos(bfqq->next_rq)) + n = &(*p)->rb_right; + else if (sector < blk_rq_pos(bfqq->next_rq)) + n = &(*p)->rb_left; + else + break; + p = n; + bfqq = NULL; + } + + *ret_parent = parent; + if (rb_link) + *rb_link = p; + + bfq_log(bfqd, "rq_pos_tree_lookup %llu: returning %d", + (long long unsigned)sector, + bfqq != NULL ? bfqq->pid : 0); + + return bfqq; +} + +static void bfq_rq_pos_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + struct rb_node **p, *parent; + struct bfq_queue *__bfqq; + + if (bfqq->pos_root != NULL) { + rb_erase(&bfqq->pos_node, bfqq->pos_root); + bfqq->pos_root = NULL; + } + + if (bfq_class_idle(bfqq)) + return; + if (!bfqq->next_rq) + return; + + bfqq->pos_root = &bfqd->rq_pos_tree; + __bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root, + blk_rq_pos(bfqq->next_rq), &parent, &p); + if (__bfqq == NULL) { + rb_link_node(&bfqq->pos_node, parent, p); + rb_insert_color(&bfqq->pos_node, bfqq->pos_root); + } else + bfqq->pos_root = NULL; +} + +/* + * Tell whether there are active queues or groups with differentiated weights. + */ +static inline bool bfq_differentiated_weights(struct bfq_data *bfqd) +{ + BUG_ON(!bfqd->hw_tag); + /* + * For weights to differ, at least one of the trees must contain + * at least two nodes. + */ + return (!RB_EMPTY_ROOT(&bfqd->queue_weights_tree) && + (bfqd->queue_weights_tree.rb_node->rb_left || + bfqd->queue_weights_tree.rb_node->rb_right) +#ifdef CONFIG_CGROUP_BFQIO + ) || + (!RB_EMPTY_ROOT(&bfqd->group_weights_tree) && + (bfqd->group_weights_tree.rb_node->rb_left || + bfqd->group_weights_tree.rb_node->rb_right) +#endif + ); +} + +/* + * If the weight-counter tree passed as input contains no counter for + * the weight of the input entity, then add that counter; otherwise just + * increment the existing counter. + * + * Note that weight-counter trees contain few nodes in mostly symmetric + * scenarios. For example, if all queues have the same weight, then the + * weight-counter tree for the queues may contain at most one node. + * This holds even if low_latency is on, because weight-raised queues + * are not inserted in the tree. + * In most scenarios, the rate at which nodes are created/destroyed + * should be low too. + */ +static void bfq_weights_tree_add(struct bfq_data *bfqd, + struct bfq_entity *entity, + struct rb_root *root) +{ + struct rb_node **new = &(root->rb_node), *parent = NULL; + + /* + * Do not insert if: + * - the device does not support queueing; + * - the entity is already associated with a counter, which happens if: + * 1) the entity is associated with a queue, 2) a request arrival + * has caused the queue to become both non-weight-raised, and hence + * change its weight, and backlogged; in this respect, each + * of the two events causes an invocation of this function, + * 3) this is the invocation of this function caused by the second + * event. This second invocation is actually useless, and we handle + * this fact by exiting immediately. More efficient or clearer + * solutions might possibly be adopted. + */ + if (!bfqd->hw_tag || entity->weight_counter) + return; + + while (*new) { + struct bfq_weight_counter *__counter = container_of(*new, + struct bfq_weight_counter, + weights_node); + parent = *new; + + if (entity->weight == __counter->weight) { + entity->weight_counter = __counter; + goto inc_counter; + } + if (entity->weight < __counter->weight) + new = &((*new)->rb_left); + else + new = &((*new)->rb_right); + } + + entity->weight_counter = kzalloc(sizeof(struct bfq_weight_counter), + GFP_ATOMIC); + entity->weight_counter->weight = entity->weight; + rb_link_node(&entity->weight_counter->weights_node, parent, new); + rb_insert_color(&entity->weight_counter->weights_node, root); + +inc_counter: + entity->weight_counter->num_active++; +} + +/* + * Decrement the weight counter associated with the entity, and, if the + * counter reaches 0, remove the counter from the tree. + * See the comments to the function bfq_weights_tree_add() for considerations + * about overhead. + */ +static void bfq_weights_tree_remove(struct bfq_data *bfqd, + struct bfq_entity *entity, + struct rb_root *root) +{ + /* + * Check whether the entity is actually associated with a counter. + * In fact, the device may not be considered NCQ-capable for a while, + * which implies that no insertion in the weight trees is performed, + * after which the device may start to be deemed NCQ-capable, and hence + * this function may start to be invoked. This may cause the function + * to be invoked for entities that are not associated with any counter. + */ + if (!entity->weight_counter) + return; + + BUG_ON(RB_EMPTY_ROOT(root)); + BUG_ON(entity->weight_counter->weight != entity->weight); + + BUG_ON(!entity->weight_counter->num_active); + entity->weight_counter->num_active--; + if (entity->weight_counter->num_active > 0) + goto reset_entity_pointer; + + rb_erase(&entity->weight_counter->weights_node, root); + kfree(entity->weight_counter); + +reset_entity_pointer: + entity->weight_counter = NULL; +} + +static struct request *bfq_find_next_rq(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + struct request *last) +{ + struct rb_node *rbnext = rb_next(&last->rb_node); + struct rb_node *rbprev = rb_prev(&last->rb_node); + struct request *next = NULL, *prev = NULL; + + BUG_ON(RB_EMPTY_NODE(&last->rb_node)); + + if (rbprev != NULL) + prev = rb_entry_rq(rbprev); + + if (rbnext != NULL) + next = rb_entry_rq(rbnext); + else { + rbnext = rb_first(&bfqq->sort_list); + if (rbnext && rbnext != &last->rb_node) + next = rb_entry_rq(rbnext); + } + + return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last)); +} + +/* see the definition of bfq_async_charge_factor for details */ +static inline unsigned long bfq_serv_to_charge(struct request *rq, + struct bfq_queue *bfqq) +{ + return blk_rq_sectors(rq) * + (1 + ((!bfq_bfqq_sync(bfqq)) * (bfqq->wr_coeff == 1) * + bfq_async_charge_factor)); +} + +/** + * bfq_updated_next_req - update the queue after a new next_rq selection. + * @bfqd: the device data the queue belongs to. + * @bfqq: the queue to update. + * + * If the first request of a queue changes we make sure that the queue + * has enough budget to serve at least its first request (if the + * request has grown). We do this because if the queue has not enough + * budget for its first request, it has to go through two dispatch + * rounds to actually get it dispatched. + */ +static void bfq_updated_next_req(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + struct bfq_service_tree *st = bfq_entity_service_tree(entity); + struct request *next_rq = bfqq->next_rq; + unsigned long new_budget; + + if (next_rq == NULL) + return; + + if (bfqq == bfqd->in_service_queue) + /* + * In order not to break guarantees, budgets cannot be + * changed after an entity has been selected. + */ + return; + + BUG_ON(entity->tree != &st->active); + BUG_ON(entity == entity->sched_data->in_service_entity); + + new_budget = max_t(unsigned long, bfqq->max_budget, + bfq_serv_to_charge(next_rq, bfqq)); + if (entity->budget != new_budget) { + entity->budget = new_budget; + bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu", + new_budget); + bfq_activate_bfqq(bfqd, bfqq); + } +} + +static inline unsigned int bfq_wr_duration(struct bfq_data *bfqd) +{ + u64 dur; + + if (bfqd->bfq_wr_max_time > 0) + return bfqd->bfq_wr_max_time; + + dur = bfqd->RT_prod; + do_div(dur, bfqd->peak_rate); + + return dur; +} + +static inline unsigned +bfq_bfqq_cooperations(struct bfq_queue *bfqq) +{ + return bfqq->bic ? bfqq->bic->cooperations : 0; +} + +static inline void +bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_io_cq *bic) +{ + if (bic->saved_idle_window) + bfq_mark_bfqq_idle_window(bfqq); + else + bfq_clear_bfqq_idle_window(bfqq); + if (bic->saved_IO_bound) + bfq_mark_bfqq_IO_bound(bfqq); + else + bfq_clear_bfqq_IO_bound(bfqq); + /* Assuming that the flag in_large_burst is already correctly set */ + if (bic->wr_time_left && bfqq->bfqd->low_latency && + !bfq_bfqq_in_large_burst(bfqq) && + bic->cooperations < bfqq->bfqd->bfq_coop_thresh) { + /* + * Start a weight raising period with the duration given by + * the raising_time_left snapshot. + */ + if (bfq_bfqq_busy(bfqq)) + bfqq->bfqd->wr_busy_queues++; + bfqq->wr_coeff = bfqq->bfqd->bfq_wr_coeff; + bfqq->wr_cur_max_time = bic->wr_time_left; + bfqq->last_wr_start_finish = jiffies; + bfqq->entity.ioprio_changed = 1; + } + /* + * Clear wr_time_left to prevent bfq_bfqq_save_state() from + * getting confused about the queue's need of a weight-raising + * period. + */ + bic->wr_time_left = 0; +} + +/* Must be called with the queue_lock held. */ +static int bfqq_process_refs(struct bfq_queue *bfqq) +{ + int process_refs, io_refs; + + io_refs = bfqq->allocated[READ] + bfqq->allocated[WRITE]; + process_refs = atomic_read(&bfqq->ref) - io_refs - bfqq->entity.on_st; + BUG_ON(process_refs < 0); + return process_refs; +} + +/* Empty burst list and add just bfqq (see comments to bfq_handle_burst) */ +static inline void bfq_reset_burst_list(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + struct bfq_queue *item; + struct hlist_node *pos, *n; + + hlist_for_each_entry_safe(item, pos, n, + &bfqd->burst_list, burst_list_node) + hlist_del_init(&item->burst_list_node); + hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list); + bfqd->burst_size = 1; +} + +/* Add bfqq to the list of queues in current burst (see bfq_handle_burst) */ +static void bfq_add_to_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + /* Increment burst size to take into account also bfqq */ + bfqd->burst_size++; + + if (bfqd->burst_size == bfqd->bfq_large_burst_thresh) { + struct bfq_queue *pos, *bfqq_item; + struct hlist_node *p, *n; + + /* + * Enough queues have been activated shortly after each + * other to consider this burst as large. + */ + bfqd->large_burst = true; + + /* + * We can now mark all queues in the burst list as + * belonging to a large burst. + */ + hlist_for_each_entry(bfqq_item, n, &bfqd->burst_list, + burst_list_node) + bfq_mark_bfqq_in_large_burst(bfqq_item); + bfq_mark_bfqq_in_large_burst(bfqq); + + /* + * From now on, and until the current burst finishes, any + * new queue being activated shortly after the last queue + * was inserted in the burst can be immediately marked as + * belonging to a large burst. So the burst list is not + * needed any more. Remove it. + */ + hlist_for_each_entry_safe(pos, p, n, &bfqd->burst_list, + burst_list_node) + hlist_del_init(&pos->burst_list_node); + } else /* burst not yet large: add bfqq to the burst list */ + hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list); +} + +/* + * If many queues happen to become active shortly after each other, then, + * to help the processes associated to these queues get their job done as + * soon as possible, it is usually better to not grant either weight-raising + * or device idling to these queues. In this comment we describe, firstly, + * the reasons why this fact holds, and, secondly, the next function, which + * implements the main steps needed to properly mark these queues so that + * they can then be treated in a different way. + * + * As for the terminology, we say that a queue becomes active, i.e., + * switches from idle to backlogged, either when it is created (as a + * consequence of the arrival of an I/O request), or, if already existing, + * when a new request for the queue arrives while the queue is idle. + * Bursts of activations, i.e., activations of different queues occurring + * shortly after each other, are typically caused by services or applications + * that spawn or reactivate many parallel threads/processes. Examples are + * systemd during boot or git grep. + * + * These services or applications benefit mostly from a high throughput: + * the quicker the requests of the activated queues are cumulatively served, + * the sooner the target job of these queues gets completed. As a consequence, + * weight-raising any of these queues, which also implies idling the device + * for it, is almost always counterproductive: in most cases it just lowers + * throughput. + * + * On the other hand, a burst of activations may be also caused by the start + * of an application that does not consist in a lot of parallel I/O-bound + * threads. In fact, with a complex application, the burst may be just a + * consequence of the fact that several processes need to be executed to + * start-up the application. To start an application as quickly as possible, + * the best thing to do is to privilege the I/O related to the application + * with respect to all other I/O. Therefore, the best strategy to start as + * quickly as possible an application that causes a burst of activations is + * to weight-raise all the queues activated during the burst. This is the + * exact opposite of the best strategy for the other type of bursts. + * + * In the end, to take the best action for each of the two cases, the two + * types of bursts need to be distinguished. Fortunately, this seems + * relatively easy to do, by looking at the sizes of the bursts. In + * particular, we found a threshold such that bursts with a larger size + * than that threshold are apparently caused only by services or commands + * such as systemd or git grep. For brevity, hereafter we call just 'large' + * these bursts. BFQ *does not* weight-raise queues whose activations occur + * in a large burst. In addition, for each of these queues BFQ performs or + * does not perform idling depending on which choice boosts the throughput + * most. The exact choice depends on the device and request pattern at + * hand. + * + * Turning back to the next function, it implements all the steps needed + * to detect the occurrence of a large burst and to properly mark all the + * queues belonging to it (so that they can then be treated in a different + * way). This goal is achieved by maintaining a special "burst list" that + * holds, temporarily, the queues that belong to the burst in progress. The + * list is then used to mark these queues as belonging to a large burst if + * the burst does become large. The main steps are the following. + * + * . when the very first queue is activated, the queue is inserted into the + * list (as it could be the first queue in a possible burst) + * + * . if the current burst has not yet become large, and a queue Q that does + * not yet belong to the burst is activated shortly after the last time + * at which a new queue entered the burst list, then the function appends + * Q to the burst list + * + * . if, as a consequence of the previous step, the burst size reaches + * the large-burst threshold, then + * + * . all the queues in the burst list are marked as belonging to a + * large burst + * + * . the burst list is deleted; in fact, the burst list already served + * its purpose (keeping temporarily track of the queues in a burst, + * so as to be able to mark them as belonging to a large burst in the + * previous sub-step), and now is not needed any more + * + * . the device enters a large-burst mode + * + * . if a queue Q that does not belong to the burst is activated while + * the device is in large-burst mode and shortly after the last time + * at which a queue either entered the burst list or was marked as + * belonging to the current large burst, then Q is immediately marked + * as belonging to a large burst. + * + * . if a queue Q that does not belong to the burst is activated a while + * later, i.e., not shortly after, than the last time at which a queue + * either entered the burst list or was marked as belonging to the + * current large burst, then the current burst is deemed as finished and: + * + * . the large-burst mode is reset if set + * + * . the burst list is emptied + * + * . Q is inserted in the burst list, as Q may be the first queue + * in a possible new burst (then the burst list contains just Q + * after this step). + */ +static void bfq_handle_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq, + bool idle_for_long_time) +{ + /* + * If bfqq happened to be activated in a burst, but has been idle + * for at least as long as an interactive queue, then we assume + * that, in the overall I/O initiated in the burst, the I/O + * associated to bfqq is finished. So bfqq does not need to be + * treated as a queue belonging to a burst anymore. Accordingly, + * we reset bfqq's in_large_burst flag if set, and remove bfqq + * from the burst list if it's there. We do not decrement instead + * burst_size, because the fact that bfqq does not need to belong + * to the burst list any more does not invalidate the fact that + * bfqq may have been activated during the current burst. + */ + if (idle_for_long_time) { + hlist_del_init(&bfqq->burst_list_node); + bfq_clear_bfqq_in_large_burst(bfqq); + } + + /* + * If bfqq is already in the burst list or is part of a large + * burst, then there is nothing else to do. + */ + if (!hlist_unhashed(&bfqq->burst_list_node) || + bfq_bfqq_in_large_burst(bfqq)) + return; + + /* + * If bfqq's activation happens late enough, then the current + * burst is finished, and related data structures must be reset. + * + * In this respect, consider the special case where bfqq is the very + * first queue being activated. In this case, last_ins_in_burst is + * not yet significant when we get here. But it is easy to verify + * that, whether or not the following condition is true, bfqq will + * end up being inserted into the burst list. In particular the + * list will happen to contain only bfqq. And this is exactly what + * has to happen, as bfqq may be the first queue in a possible + * burst. + */ + if (time_is_before_jiffies(bfqd->last_ins_in_burst + + bfqd->bfq_burst_interval)) { + bfqd->large_burst = false; + bfq_reset_burst_list(bfqd, bfqq); + return; + } + + /* + * If we get here, then bfqq is being activated shortly after the + * last queue. So, if the current burst is also large, we can mark + * bfqq as belonging to this large burst immediately. + */ + if (bfqd->large_burst) { + bfq_mark_bfqq_in_large_burst(bfqq); + return; + } + + /* + * If we get here, then a large-burst state has not yet been + * reached, but bfqq is being activated shortly after the last + * queue. Then we add bfqq to the burst. + */ + bfq_add_to_burst(bfqd, bfqq); +} + +static void bfq_add_request(struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + struct bfq_entity *entity = &bfqq->entity; + struct bfq_data *bfqd = bfqq->bfqd; + struct request *next_rq, *prev; + unsigned long old_wr_coeff = bfqq->wr_coeff; + bool interactive = false; + + bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq)); + bfqq->queued[rq_is_sync(rq)]++; + bfqd->queued++; + + elv_rb_add(&bfqq->sort_list, rq); + + /* + * Check if this request is a better next-serve candidate. + */ + prev = bfqq->next_rq; + next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position); + BUG_ON(next_rq == NULL); + bfqq->next_rq = next_rq; + + /* + * Adjust priority tree position, if next_rq changes. + */ + if (prev != bfqq->next_rq) + bfq_rq_pos_tree_add(bfqd, bfqq); + + if (!bfq_bfqq_busy(bfqq)) { + bool soft_rt, coop_or_in_burst, + idle_for_long_time = time_is_before_jiffies( + bfqq->budget_timeout + + bfqd->bfq_wr_min_idle_time); + + if (bfq_bfqq_sync(bfqq)) { + bool already_in_burst = + !hlist_unhashed(&bfqq->burst_list_node) || + bfq_bfqq_in_large_burst(bfqq); + bfq_handle_burst(bfqd, bfqq, idle_for_long_time); + /* + * If bfqq was not already in the current burst, + * then, at this point, bfqq either has been + * added to the current burst or has caused the + * current burst to terminate. In particular, in + * the second case, bfqq has become the first + * queue in a possible new burst. + * In both cases last_ins_in_burst needs to be + * moved forward. + */ + if (!already_in_burst) + bfqd->last_ins_in_burst = jiffies; + } + + coop_or_in_burst = bfq_bfqq_in_large_burst(bfqq) || + bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh; + soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 && + !coop_or_in_burst && + time_is_before_jiffies(bfqq->soft_rt_next_start); + interactive = !coop_or_in_burst && idle_for_long_time; + entity->budget = max_t(unsigned long, bfqq->max_budget, + bfq_serv_to_charge(next_rq, bfqq)); + + if (!bfq_bfqq_IO_bound(bfqq)) { + if (time_before(jiffies, + RQ_BIC(rq)->ttime.last_end_request + + bfqd->bfq_slice_idle)) { + bfqq->requests_within_timer++; + if (bfqq->requests_within_timer >= + bfqd->bfq_requests_within_timer) + bfq_mark_bfqq_IO_bound(bfqq); + } else + bfqq->requests_within_timer = 0; + } + + if (!bfqd->low_latency) + goto add_bfqq_busy; + + if (bfq_bfqq_just_split(bfqq)) + goto set_ioprio_changed; + + /* + * If the queue: + * - is not being boosted, + * - has been idle for enough time, + * - is not a sync queue or is linked to a bfq_io_cq (it is + * shared "for its nature" or it is not shared and its + * requests have not been redirected to a shared queue) + * start a weight-raising period. + */ + if (old_wr_coeff == 1 && (interactive || soft_rt) && + (!bfq_bfqq_sync(bfqq) || bfqq->bic != NULL)) { + bfqq->wr_coeff = bfqd->bfq_wr_coeff; + if (interactive) + bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); + else + bfqq->wr_cur_max_time = + bfqd->bfq_wr_rt_max_time; + bfq_log_bfqq(bfqd, bfqq, + "wrais starting at %lu, rais_max_time %u", + jiffies, + jiffies_to_msecs(bfqq->wr_cur_max_time)); + } else if (old_wr_coeff > 1) { + if (interactive) + bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); + else if (coop_or_in_burst || + (bfqq->wr_cur_max_time == + bfqd->bfq_wr_rt_max_time && + !soft_rt)) { + bfqq->wr_coeff = 1; + bfq_log_bfqq(bfqd, bfqq, + "wrais ending at %lu, rais_max_time %u", + jiffies, + jiffies_to_msecs(bfqq-> + wr_cur_max_time)); + } else if (time_before( + bfqq->last_wr_start_finish + + bfqq->wr_cur_max_time, + jiffies + + bfqd->bfq_wr_rt_max_time) && + soft_rt) { + /* + * + * The remaining weight-raising time is lower + * than bfqd->bfq_wr_rt_max_time, which means + * that the application is enjoying weight + * raising either because deemed soft-rt in + * the near past, or because deemed interactive + * a long ago. + * In both cases, resetting now the current + * remaining weight-raising time for the + * application to the weight-raising duration + * for soft rt applications would not cause any + * latency increase for the application (as the + * new duration would be higher than the + * remaining time). + * + * In addition, the application is now meeting + * the requirements for being deemed soft rt. + * In the end we can correctly and safely + * (re)charge the weight-raising duration for + * the application with the weight-raising + * duration for soft rt applications. + * + * In particular, doing this recharge now, i.e., + * before the weight-raising period for the + * application finishes, reduces the probability + * of the following negative scenario: + * 1) the weight of a soft rt application is + * raised at startup (as for any newly + * created application), + * 2) since the application is not interactive, + * at a certain time weight-raising is + * stopped for the application, + * 3) at that time the application happens to + * still have pending requests, and hence + * is destined to not have a chance to be + * deemed soft rt before these requests are + * completed (see the comments to the + * function bfq_bfqq_softrt_next_start() + * for details on soft rt detection), + * 4) these pending requests experience a high + * latency because the application is not + * weight-raised while they are pending. + */ + bfqq->last_wr_start_finish = jiffies; + bfqq->wr_cur_max_time = + bfqd->bfq_wr_rt_max_time; + } + } +set_ioprio_changed: + if (old_wr_coeff != bfqq->wr_coeff) + entity->ioprio_changed = 1; +add_bfqq_busy: + bfqq->last_idle_bklogged = jiffies; + bfqq->service_from_backlogged = 0; + bfq_clear_bfqq_softrt_update(bfqq); + bfq_add_bfqq_busy(bfqd, bfqq); + } else { + if (bfqd->low_latency && old_wr_coeff == 1 && !rq_is_sync(rq) && + time_is_before_jiffies( + bfqq->last_wr_start_finish + + bfqd->bfq_wr_min_inter_arr_async)) { + bfqq->wr_coeff = bfqd->bfq_wr_coeff; + bfqq->wr_cur_max_time = bfq_wr_duration(bfqd); + + bfqd->wr_busy_queues++; + entity->ioprio_changed = 1; + bfq_log_bfqq(bfqd, bfqq, + "non-idle wrais starting at %lu, rais_max_time %u", + jiffies, + jiffies_to_msecs(bfqq->wr_cur_max_time)); + } + if (prev != bfqq->next_rq) + bfq_updated_next_req(bfqd, bfqq); + } + + if (bfqd->low_latency && + (old_wr_coeff == 1 || bfqq->wr_coeff == 1 || interactive)) + bfqq->last_wr_start_finish = jiffies; +} + +static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd, + struct bio *bio) +{ + struct task_struct *tsk = current; + struct bfq_io_cq *bic; + struct bfq_queue *bfqq; + + bic = bfq_bic_lookup(bfqd, tsk->io_context); + if (bic == NULL) + return NULL; + + bfqq = bic_to_bfqq(bic, bfq_bio_sync(bio)); + if (bfqq != NULL) { + sector_t sector = bio->bi_sector + bio_sectors(bio); + + return elv_rb_find(&bfqq->sort_list, sector); + } + + return NULL; +} + +static void bfq_activate_request(struct request_queue *q, struct request *rq) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + + bfqd->rq_in_driver++; + bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq); + bfq_log(bfqd, "activate_request: new bfqd->last_position %llu", + (long long unsigned)bfqd->last_position); +} + +static inline void bfq_deactivate_request(struct request_queue *q, + struct request *rq) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + + BUG_ON(bfqd->rq_in_driver == 0); + bfqd->rq_in_driver--; +} + +static void bfq_remove_request(struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + struct bfq_data *bfqd = bfqq->bfqd; + const int sync = rq_is_sync(rq); + + if (bfqq->next_rq == rq) { + bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq); + bfq_updated_next_req(bfqd, bfqq); + } + + list_del_init(&rq->queuelist); + BUG_ON(bfqq->queued[sync] == 0); + bfqq->queued[sync]--; + bfqd->queued--; + elv_rb_del(&bfqq->sort_list, rq); + + if (RB_EMPTY_ROOT(&bfqq->sort_list)) { + if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue) + bfq_del_bfqq_busy(bfqd, bfqq, 1); + /* + * Remove queue from request-position tree as it is empty. + */ + if (bfqq->pos_root != NULL) { + rb_erase(&bfqq->pos_node, bfqq->pos_root); + bfqq->pos_root = NULL; + } + } + + if (rq->cmd_flags & REQ_META) { + BUG_ON(bfqq->meta_pending == 0); + bfqq->meta_pending--; + } +} + +static int bfq_merge(struct request_queue *q, struct request **req, + struct bio *bio) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct request *__rq; + + __rq = bfq_find_rq_fmerge(bfqd, bio); + if (__rq != NULL && elv_rq_merge_ok(__rq, bio)) { + *req = __rq; + return ELEVATOR_FRONT_MERGE; + } + + return ELEVATOR_NO_MERGE; +} + +static void bfq_merged_request(struct request_queue *q, struct request *req, + int type) +{ + if (type == ELEVATOR_FRONT_MERGE && + rb_prev(&req->rb_node) && + blk_rq_pos(req) < + blk_rq_pos(container_of(rb_prev(&req->rb_node), + struct request, rb_node))) { + struct bfq_queue *bfqq = RQ_BFQQ(req); + struct bfq_data *bfqd = bfqq->bfqd; + struct request *prev, *next_rq; + + /* Reposition request in its sort_list */ + elv_rb_del(&bfqq->sort_list, req); + elv_rb_add(&bfqq->sort_list, req); + /* Choose next request to be served for bfqq */ + prev = bfqq->next_rq; + next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req, + bfqd->last_position); + BUG_ON(next_rq == NULL); + bfqq->next_rq = next_rq; + /* + * If next_rq changes, update both the queue's budget to + * fit the new request and the queue's position in its + * rq_pos_tree. + */ + if (prev != bfqq->next_rq) { + bfq_updated_next_req(bfqd, bfqq); + bfq_rq_pos_tree_add(bfqd, bfqq); + } + } +} + +static void bfq_merged_requests(struct request_queue *q, struct request *rq, + struct request *next) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + + /* + * Reposition in fifo if next is older than rq. + */ + if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) && + time_before(rq_fifo_time(next), rq_fifo_time(rq))) { + list_move(&rq->queuelist, &next->queuelist); + rq_set_fifo_time(rq, rq_fifo_time(next)); + } + + if (bfqq->next_rq == next) + bfqq->next_rq = rq; + + bfq_remove_request(next); +} + +/* Must be called with bfqq != NULL */ +static inline void bfq_bfqq_end_wr(struct bfq_queue *bfqq) +{ + BUG_ON(bfqq == NULL); + if (bfq_bfqq_busy(bfqq)) + bfqq->bfqd->wr_busy_queues--; + bfqq->wr_coeff = 1; + bfqq->wr_cur_max_time = 0; + /* Trigger a weight change on the next activation of the queue */ + bfqq->entity.ioprio_changed = 1; +} + +static void bfq_end_wr_async_queues(struct bfq_data *bfqd, + struct bfq_group *bfqg) +{ + int i, j; + + for (i = 0; i < 2; i++) + for (j = 0; j < IOPRIO_BE_NR; j++) + if (bfqg->async_bfqq[i][j] != NULL) + bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]); + if (bfqg->async_idle_bfqq != NULL) + bfq_bfqq_end_wr(bfqg->async_idle_bfqq); +} + +static void bfq_end_wr(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq; + + spin_lock_irq(bfqd->queue->queue_lock); + + list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) + bfq_bfqq_end_wr(bfqq); + list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list) + bfq_bfqq_end_wr(bfqq); + bfq_end_wr_async(bfqd); + + spin_unlock_irq(bfqd->queue->queue_lock); +} + +static inline sector_t bfq_io_struct_pos(void *io_struct, bool request) +{ + if (request) + return blk_rq_pos(io_struct); + else + return ((struct bio *)io_struct)->bi_sector; +} + +static inline sector_t bfq_dist_from(sector_t pos1, + sector_t pos2) +{ + if (pos1 >= pos2) + return pos1 - pos2; + else + return pos2 - pos1; +} + +static inline int bfq_rq_close_to_sector(void *io_struct, bool request, + sector_t sector) +{ + return bfq_dist_from(bfq_io_struct_pos(io_struct, request), sector) <= + BFQQ_SEEK_THR; +} + +static struct bfq_queue *bfqq_close(struct bfq_data *bfqd, sector_t sector) +{ + struct rb_root *root = &bfqd->rq_pos_tree; + struct rb_node *parent, *node; + struct bfq_queue *__bfqq; + + if (RB_EMPTY_ROOT(root)) + return NULL; + + /* + * First, if we find a request starting at the end of the last + * request, choose it. + */ + __bfqq = bfq_rq_pos_tree_lookup(bfqd, root, sector, &parent, NULL); + if (__bfqq != NULL) + return __bfqq; + + /* + * If the exact sector wasn't found, the parent of the NULL leaf + * will contain the closest sector (rq_pos_tree sorted by + * next_request position). + */ + __bfqq = rb_entry(parent, struct bfq_queue, pos_node); + if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector)) + return __bfqq; + + if (blk_rq_pos(__bfqq->next_rq) < sector) + node = rb_next(&__bfqq->pos_node); + else + node = rb_prev(&__bfqq->pos_node); + if (node == NULL) + return NULL; + + __bfqq = rb_entry(node, struct bfq_queue, pos_node); + if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector)) + return __bfqq; + + return NULL; +} + +/* + * bfqd - obvious + * cur_bfqq - passed in so that we don't decide that the current queue + * is closely cooperating with itself + * sector - used as a reference point to search for a close queue + */ +static struct bfq_queue *bfq_close_cooperator(struct bfq_data *bfqd, + struct bfq_queue *cur_bfqq, + sector_t sector) +{ + struct bfq_queue *bfqq; + + if (bfq_class_idle(cur_bfqq)) + return NULL; + if (!bfq_bfqq_sync(cur_bfqq)) + return NULL; + if (BFQQ_SEEKY(cur_bfqq)) + return NULL; + + /* If device has only one backlogged bfq_queue, don't search. */ + if (bfqd->busy_queues == 1) + return NULL; + + /* + * We should notice if some of the queues are cooperating, e.g. + * working closely on the same area of the disk. In that case, + * we can group them together and don't waste time idling. + */ + bfqq = bfqq_close(bfqd, sector); + if (bfqq == NULL || bfqq == cur_bfqq) + return NULL; + + /* + * Do not merge queues from different bfq_groups. + */ + if (bfqq->entity.parent != cur_bfqq->entity.parent) + return NULL; + + /* + * It only makes sense to merge sync queues. + */ + if (!bfq_bfqq_sync(bfqq)) + return NULL; + if (BFQQ_SEEKY(bfqq)) + return NULL; + + /* + * Do not merge queues of different priority classes. + */ + if (bfq_class_rt(bfqq) != bfq_class_rt(cur_bfqq)) + return NULL; + + return bfqq; +} + +static struct bfq_queue * +bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) +{ + int process_refs, new_process_refs; + struct bfq_queue *__bfqq; + + /* + * If there are no process references on the new_bfqq, then it is + * unsafe to follow the ->new_bfqq chain as other bfqq's in the chain + * may have dropped their last reference (not just their last process + * reference). + */ + if (!bfqq_process_refs(new_bfqq)) + return NULL; + + /* Avoid a circular list and skip interim queue merges. */ + while ((__bfqq = new_bfqq->new_bfqq)) { + if (__bfqq == bfqq) + return NULL; + new_bfqq = __bfqq; + } + + process_refs = bfqq_process_refs(bfqq); + new_process_refs = bfqq_process_refs(new_bfqq); + /* + * If the process for the bfqq has gone away, there is no + * sense in merging the queues. + */ + if (process_refs == 0 || new_process_refs == 0) + return NULL; + + bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d", + new_bfqq->pid); + + /* + * Merging is just a redirection: the requests of the process + * owning one of the two queues are redirected to the other queue. + * The latter queue, in its turn, is set as shared if this is the + * first time that the requests of some process are redirected to + * it. + * + * We redirect bfqq to new_bfqq and not the opposite, because we + * are in the context of the process owning bfqq, hence we have + * the io_cq of this process. So we can immediately configure this + * io_cq to redirect the requests of the process to new_bfqq. + * + * NOTE, even if new_bfqq coincides with the in-service queue, the + * io_cq of new_bfqq is not available, because, if the in-service + * queue is shared, bfqd->in_service_bic may not point to the + * io_cq of the in-service queue. + * Redirecting the requests of the process owning bfqq to the + * currently in-service queue is in any case the best option, as + * we feed the in-service queue with new requests close to the + * last request served and, by doing so, hopefully increase the + * throughput. + */ + bfqq->new_bfqq = new_bfqq; + atomic_add(process_refs, &new_bfqq->ref); + return new_bfqq; +} + +/* + * Attempt to schedule a merge of bfqq with the currently in-service queue + * or with a close queue among the scheduled queues. + * Return NULL if no merge was scheduled, a pointer to the shared bfq_queue + * structure otherwise. + * + * The OOM queue is not allowed to participate to cooperation: in fact, since + * the requests temporarily redirected to the OOM queue could be redirected + * again to dedicated queues at any time, the state needed to correctly + * handle merging with the OOM queue would be quite complex and expensive + * to maintain. Besides, in such a critical condition as an out of memory, + * the benefits of queue merging may be little relevant, or even negligible. + */ +static struct bfq_queue * +bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, + void *io_struct, bool request) +{ + struct bfq_queue *in_service_bfqq, *new_bfqq; + + if (bfqq->new_bfqq) + return bfqq->new_bfqq; + + if (!io_struct || unlikely(bfqq == &bfqd->oom_bfqq)) + return NULL; + + in_service_bfqq = bfqd->in_service_queue; + + if (in_service_bfqq == NULL || in_service_bfqq == bfqq || + !bfqd->in_service_bic || + unlikely(in_service_bfqq == &bfqd->oom_bfqq)) + goto check_scheduled; + + if (bfq_class_idle(in_service_bfqq) || bfq_class_idle(bfqq)) + goto check_scheduled; + + if (bfq_class_rt(in_service_bfqq) != bfq_class_rt(bfqq)) + goto check_scheduled; + + if (in_service_bfqq->entity.parent != bfqq->entity.parent) + goto check_scheduled; + + if (bfq_rq_close_to_sector(io_struct, request, bfqd->last_position) && + bfq_bfqq_sync(in_service_bfqq) && bfq_bfqq_sync(bfqq)) { + new_bfqq = bfq_setup_merge(bfqq, in_service_bfqq); + if (new_bfqq != NULL) + return new_bfqq; /* Merge with in-service queue */ + } + + /* + * Check whether there is a cooperator among currently scheduled + * queues. The only thing we need is that the bio/request is not + * NULL, as we need it to establish whether a cooperator exists. + */ +check_scheduled: + new_bfqq = bfq_close_cooperator(bfqd, bfqq, + bfq_io_struct_pos(io_struct, request)); + if (new_bfqq && likely(new_bfqq != &bfqd->oom_bfqq)) + return bfq_setup_merge(bfqq, new_bfqq); + + return NULL; +} + +static inline void +bfq_bfqq_save_state(struct bfq_queue *bfqq) +{ + /* + * If bfqq->bic == NULL, the queue is already shared or its requests + * have already been redirected to a shared queue; both idle window + * and weight raising state have already been saved. Do nothing. + */ + if (bfqq->bic == NULL) + return; + if (bfqq->bic->wr_time_left) + /* + * This is the queue of a just-started process, and would + * deserve weight raising: we set wr_time_left to the full + * weight-raising duration to trigger weight-raising when + * and if the queue is split and the first request of the + * queue is enqueued. + */ + bfqq->bic->wr_time_left = bfq_wr_duration(bfqq->bfqd); + else if (bfqq->wr_coeff > 1) { + unsigned long wr_duration = + jiffies - bfqq->last_wr_start_finish; + /* + * It may happen that a queue's weight raising period lasts + * longer than its wr_cur_max_time, as weight raising is + * handled only when a request is enqueued or dispatched (it + * does not use any timer). If the weight raising period is + * about to end, don't save it. + */ + if (bfqq->wr_cur_max_time <= wr_duration) + bfqq->bic->wr_time_left = 0; + else + bfqq->bic->wr_time_left = + bfqq->wr_cur_max_time - wr_duration; + /* + * The bfq_queue is becoming shared or the requests of the + * process owning the queue are being redirected to a shared + * queue. Stop the weight raising period of the queue, as in + * both cases it should not be owned by an interactive or + * soft real-time application. + */ + bfq_bfqq_end_wr(bfqq); + } else + bfqq->bic->wr_time_left = 0; + bfqq->bic->saved_idle_window = bfq_bfqq_idle_window(bfqq); + bfqq->bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq); + bfqq->bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq); + bfqq->bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node); + bfqq->bic->cooperations++; + bfqq->bic->failed_cooperations = 0; +} + +static inline void +bfq_get_bic_reference(struct bfq_queue *bfqq) +{ + /* + * If bfqq->bic has a non-NULL value, the bic to which it belongs + * is about to begin using a shared bfq_queue. + */ + if (bfqq->bic) + atomic_long_inc(&bfqq->bic->icq.ioc->refcount); +} + +static void +bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic, + struct bfq_queue *bfqq, struct bfq_queue *new_bfqq) +{ + bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu", + (long unsigned)new_bfqq->pid); + /* Save weight raising and idle window of the merged queues */ + bfq_bfqq_save_state(bfqq); + bfq_bfqq_save_state(new_bfqq); + if (bfq_bfqq_IO_bound(bfqq)) + bfq_mark_bfqq_IO_bound(new_bfqq); + bfq_clear_bfqq_IO_bound(bfqq); + /* + * Grab a reference to the bic, to prevent it from being destroyed + * before being possibly touched by a bfq_split_bfqq(). + */ + bfq_get_bic_reference(bfqq); + bfq_get_bic_reference(new_bfqq); + /* + * Merge queues (that is, let bic redirect its requests to new_bfqq) + */ + bic_set_bfqq(bic, new_bfqq, 1); + bfq_mark_bfqq_coop(new_bfqq); + /* + * new_bfqq now belongs to at least two bics (it is a shared queue): + * set new_bfqq->bic to NULL. bfqq either: + * - does not belong to any bic any more, and hence bfqq->bic must + * be set to NULL, or + * - is a queue whose owning bics have already been redirected to a + * different queue, hence the queue is destined to not belong to + * any bic soon and bfqq->bic is already NULL (therefore the next + * assignment causes no harm). + */ + new_bfqq->bic = NULL; + bfqq->bic = NULL; + bfq_put_queue(bfqq); +} + +static inline void bfq_bfqq_increase_failed_cooperations(struct bfq_queue *bfqq) +{ + struct bfq_io_cq *bic = bfqq->bic; + struct bfq_data *bfqd = bfqq->bfqd; + + if (bic && bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh) { + bic->failed_cooperations++; + if (bic->failed_cooperations >= bfqd->bfq_failed_cooperations) + bic->cooperations = 0; + } +} + +static int bfq_allow_merge(struct request_queue *q, struct request *rq, + struct bio *bio) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct bfq_io_cq *bic; + struct bfq_queue *bfqq, *new_bfqq; + + /* + * Disallow merge of a sync bio into an async request. + */ + if (bfq_bio_sync(bio) && !rq_is_sync(rq)) + return 0; + + /* + * Lookup the bfqq that this bio will be queued with. Allow + * merge only if rq is queued there. + * Queue lock is held here. + */ + bic = bfq_bic_lookup(bfqd, current->io_context); + if (bic == NULL) + return 0; + + bfqq = bic_to_bfqq(bic, bfq_bio_sync(bio)); + /* + * We take advantage of this function to perform an early merge + * of the queues of possible cooperating processes. + */ + if (bfqq != NULL) { + new_bfqq = bfq_setup_cooperator(bfqd, bfqq, bio, false); + if (new_bfqq != NULL) { + bfq_merge_bfqqs(bfqd, bic, bfqq, new_bfqq); + /* + * If we get here, the bio will be queued in the + * shared queue, i.e., new_bfqq, so use new_bfqq + * to decide whether bio and rq can be merged. + */ + bfqq = new_bfqq; + } else + bfq_bfqq_increase_failed_cooperations(bfqq); + } + + return bfqq == RQ_BFQQ(rq); +} + +static void __bfq_set_in_service_queue(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + if (bfqq != NULL) { + bfq_mark_bfqq_must_alloc(bfqq); + bfq_mark_bfqq_budget_new(bfqq); + bfq_clear_bfqq_fifo_expire(bfqq); + + bfqd->budgets_assigned = (bfqd->budgets_assigned*7 + 256) / 8; + + bfq_log_bfqq(bfqd, bfqq, + "set_in_service_queue, cur-budget = %lu", + bfqq->entity.budget); + } + + bfqd->in_service_queue = bfqq; +} + +/* + * Get and set a new queue for service. + */ +static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq = bfq_get_next_queue(bfqd); + + __bfq_set_in_service_queue(bfqd, bfqq); + return bfqq; +} + +/* + * If enough samples have been computed, return the current max budget + * stored in bfqd, which is dynamically updated according to the + * estimated disk peak rate; otherwise return the default max budget + */ +static inline unsigned long bfq_max_budget(struct bfq_data *bfqd) +{ + if (bfqd->budgets_assigned < 194) + return bfq_default_max_budget; + else + return bfqd->bfq_max_budget; +} + +/* + * Return min budget, which is a fraction of the current or default + * max budget (trying with 1/32) + */ +static inline unsigned long bfq_min_budget(struct bfq_data *bfqd) +{ + if (bfqd->budgets_assigned < 194) + return bfq_default_max_budget / 32; + else + return bfqd->bfq_max_budget / 32; +} + +static void bfq_arm_slice_timer(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq = bfqd->in_service_queue; + struct bfq_io_cq *bic; + unsigned long sl; + + BUG_ON(!RB_EMPTY_ROOT(&bfqq->sort_list)); + + /* Processes have exited, don't wait. */ + bic = bfqd->in_service_bic; + if (bic == NULL || atomic_read(&bic->icq.ioc->nr_tasks) == 0) + return; + + bfq_mark_bfqq_wait_request(bfqq); + + /* + * We don't want to idle for seeks, but we do want to allow + * fair distribution of slice time for a process doing back-to-back + * seeks. So allow a little bit of time for him to submit a new rq. + * + * To prevent processes with (partly) seeky workloads from + * being too ill-treated, grant them a small fraction of the + * assigned budget before reducing the waiting time to + * BFQ_MIN_TT. This happened to help reduce latency. + */ + sl = bfqd->bfq_slice_idle; + /* + * Unless the queue is being weight-raised, grant only minimum idle + * time if the queue either has been seeky for long enough or has + * already proved to be constantly seeky. + */ + if (bfq_sample_valid(bfqq->seek_samples) && + ((BFQQ_SEEKY(bfqq) && bfqq->entity.service > + bfq_max_budget(bfqq->bfqd) / 8) || + bfq_bfqq_constantly_seeky(bfqq)) && bfqq->wr_coeff == 1) + sl = min(sl, msecs_to_jiffies(BFQ_MIN_TT)); + else if (bfqq->wr_coeff > 1) + sl = sl * 3; + bfqd->last_idling_start = ktime_get(); + mod_timer(&bfqd->idle_slice_timer, jiffies + sl); + bfq_log(bfqd, "arm idle: %u/%u ms", + jiffies_to_msecs(sl), jiffies_to_msecs(bfqd->bfq_slice_idle)); +} + +/* + * Set the maximum time for the in-service queue to consume its + * budget. This prevents seeky processes from lowering the disk + * throughput (always guaranteed with a time slice scheme as in CFQ). + */ +static void bfq_set_budget_timeout(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq = bfqd->in_service_queue; + unsigned int timeout_coeff; + if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time) + timeout_coeff = 1; + else + timeout_coeff = bfqq->entity.weight / bfqq->entity.orig_weight; + + bfqd->last_budget_start = ktime_get(); + + bfq_clear_bfqq_budget_new(bfqq); + bfqq->budget_timeout = jiffies + + bfqd->bfq_timeout[bfq_bfqq_sync(bfqq)] * timeout_coeff; + + bfq_log_bfqq(bfqd, bfqq, "set budget_timeout %u", + jiffies_to_msecs(bfqd->bfq_timeout[bfq_bfqq_sync(bfqq)] * + timeout_coeff)); +} + +/* + * Move request from internal lists to the request queue dispatch list. + */ +static void bfq_dispatch_insert(struct request_queue *q, struct request *rq) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct bfq_queue *bfqq = RQ_BFQQ(rq); + + /* + * For consistency, the next instruction should have been executed + * after removing the request from the queue and dispatching it. + * We execute instead this instruction before bfq_remove_request() + * (and hence introduce a temporary inconsistency), for efficiency. + * In fact, in a forced_dispatch, this prevents two counters related + * to bfqq->dispatched to risk to be uselessly decremented if bfqq + * is not in service, and then to be incremented again after + * incrementing bfqq->dispatched. + */ + bfqq->dispatched++; + bfq_remove_request(rq); + elv_dispatch_sort(q, rq); + + if (bfq_bfqq_sync(bfqq)) + bfqd->sync_flight++; +} + +/* + * Return expired entry, or NULL to just start from scratch in rbtree. + */ +static struct request *bfq_check_fifo(struct bfq_queue *bfqq) +{ + struct request *rq = NULL; + + if (bfq_bfqq_fifo_expire(bfqq)) + return NULL; + + bfq_mark_bfqq_fifo_expire(bfqq); + + if (list_empty(&bfqq->fifo)) + return NULL; + + rq = rq_entry_fifo(bfqq->fifo.next); + + if (time_before(jiffies, rq_fifo_time(rq))) + return NULL; + + return rq; +} + +static inline unsigned long bfq_bfqq_budget_left(struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + return entity->budget - entity->service; +} + +static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + BUG_ON(bfqq != bfqd->in_service_queue); + + __bfq_bfqd_reset_in_service(bfqd); + + /* + * If this bfqq is shared between multiple processes, check + * to make sure that those processes are still issuing I/Os + * within the mean seek distance. If not, it may be time to + * break the queues apart again. + */ + if (bfq_bfqq_coop(bfqq) && BFQQ_SEEKY(bfqq)) + bfq_mark_bfqq_split_coop(bfqq); + + if (RB_EMPTY_ROOT(&bfqq->sort_list)) { + /* + * Overloading budget_timeout field to store the time + * at which the queue remains with no backlog; used by + * the weight-raising mechanism. + */ + bfqq->budget_timeout = jiffies; + bfq_del_bfqq_busy(bfqd, bfqq, 1); + } else { + bfq_activate_bfqq(bfqd, bfqq); + /* + * Resort priority tree of potential close cooperators. + */ + bfq_rq_pos_tree_add(bfqd, bfqq); + } +} + +/** + * __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior. + * @bfqd: device data. + * @bfqq: queue to update. + * @reason: reason for expiration. + * + * Handle the feedback on @bfqq budget. See the body for detailed + * comments. + */ +static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + enum bfqq_expiration reason) +{ + struct request *next_rq; + unsigned long budget, min_budget; + + budget = bfqq->max_budget; + min_budget = bfq_min_budget(bfqd); + + BUG_ON(bfqq != bfqd->in_service_queue); + + bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %lu, budg left %lu", + bfqq->entity.budget, bfq_bfqq_budget_left(bfqq)); + bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %lu, min budg %lu", + budget, bfq_min_budget(bfqd)); + bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d", + bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue)); + + if (bfq_bfqq_sync(bfqq)) { + switch (reason) { + /* + * Caveat: in all the following cases we trade latency + * for throughput. + */ + case BFQ_BFQQ_TOO_IDLE: + /* + * This is the only case where we may reduce + * the budget: if there is no request of the + * process still waiting for completion, then + * we assume (tentatively) that the timer has + * expired because the batch of requests of + * the process could have been served with a + * smaller budget. Hence, betting that + * process will behave in the same way when it + * becomes backlogged again, we reduce its + * next budget. As long as we guess right, + * this budget cut reduces the latency + * experienced by the process. + * + * However, if there are still outstanding + * requests, then the process may have not yet + * issued its next request just because it is + * still waiting for the completion of some of + * the still outstanding ones. So in this + * subcase we do not reduce its budget, on the + * contrary we increase it to possibly boost + * the throughput, as discussed in the + * comments to the BUDGET_TIMEOUT case. + */ + if (bfqq->dispatched > 0) /* still outstanding reqs */ + budget = min(budget * 2, bfqd->bfq_max_budget); + else { + if (budget > 5 * min_budget) + budget -= 4 * min_budget; + else + budget = min_budget; + } + break; + case BFQ_BFQQ_BUDGET_TIMEOUT: + /* + * We double the budget here because: 1) it + * gives the chance to boost the throughput if + * this is not a seeky process (which may have + * bumped into this timeout because of, e.g., + * ZBR), 2) together with charge_full_budget + * it helps give seeky processes higher + * timestamps, and hence be served less + * frequently. + */ + budget = min(budget * 2, bfqd->bfq_max_budget); + break; + case BFQ_BFQQ_BUDGET_EXHAUSTED: + /* + * The process still has backlog, and did not + * let either the budget timeout or the disk + * idling timeout expire. Hence it is not + * seeky, has a short thinktime and may be + * happy with a higher budget too. So + * definitely increase the budget of this good + * candidate to boost the disk throughput. + */ + budget = min(budget * 4, bfqd->bfq_max_budget); + break; + case BFQ_BFQQ_NO_MORE_REQUESTS: + /* + * Leave the budget unchanged. + */ + default: + return; + } + } else /* async queue */ + /* async queues get always the maximum possible budget + * (their ability to dispatch is limited by + * @bfqd->bfq_max_budget_async_rq). + */ + budget = bfqd->bfq_max_budget; + + bfqq->max_budget = budget; + + if (bfqd->budgets_assigned >= 194 && bfqd->bfq_user_max_budget == 0 && + bfqq->max_budget > bfqd->bfq_max_budget) + bfqq->max_budget = bfqd->bfq_max_budget; + + /* + * Make sure that we have enough budget for the next request. + * Since the finish time of the bfqq must be kept in sync with + * the budget, be sure to call __bfq_bfqq_expire() after the + * update. + */ + next_rq = bfqq->next_rq; + if (next_rq != NULL) + bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget, + bfq_serv_to_charge(next_rq, bfqq)); + else + bfqq->entity.budget = bfqq->max_budget; + + bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %lu", + next_rq != NULL ? blk_rq_sectors(next_rq) : 0, + bfqq->entity.budget); +} + +static unsigned long bfq_calc_max_budget(u64 peak_rate, u64 timeout) +{ + unsigned long max_budget; + + /* + * The max_budget calculated when autotuning is equal to the + * amount of sectors transfered in timeout_sync at the + * estimated peak rate. + */ + max_budget = (unsigned long)(peak_rate * 1000 * + timeout >> BFQ_RATE_SHIFT); + + return max_budget; +} + +/* + * In addition to updating the peak rate, checks whether the process + * is "slow", and returns 1 if so. This slow flag is used, in addition + * to the budget timeout, to reduce the amount of service provided to + * seeky processes, and hence reduce their chances to lower the + * throughput. See the code for more details. + */ +static int bfq_update_peak_rate(struct bfq_data *bfqd, struct bfq_queue *bfqq, + int compensate, enum bfqq_expiration reason) +{ + u64 bw, usecs, expected, timeout; + ktime_t delta; + int update = 0; + + if (!bfq_bfqq_sync(bfqq) || bfq_bfqq_budget_new(bfqq)) + return 0; + + if (compensate) + delta = bfqd->last_idling_start; + else + delta = ktime_get(); + delta = ktime_sub(delta, bfqd->last_budget_start); + usecs = ktime_to_us(delta); + + /* Don't trust short/unrealistic values. */ + if (usecs < 100 || usecs >= LONG_MAX) + return 0; + + /* + * Calculate the bandwidth for the last slice. We use a 64 bit + * value to store the peak rate, in sectors per usec in fixed + * point math. We do so to have enough precision in the estimate + * and to avoid overflows. + */ + bw = (u64)bfqq->entity.service << BFQ_RATE_SHIFT; + do_div(bw, (unsigned long)usecs); + + timeout = jiffies_to_msecs(bfqd->bfq_timeout[BLK_RW_SYNC]); + + /* + * Use only long (> 20ms) intervals to filter out spikes for + * the peak rate estimation. + */ + if (usecs > 20000) { + if (bw > bfqd->peak_rate || + (!BFQQ_SEEKY(bfqq) && + reason == BFQ_BFQQ_BUDGET_TIMEOUT)) { + bfq_log(bfqd, "measured bw =%llu", bw); + /* + * To smooth oscillations use a low-pass filter with + * alpha=7/8, i.e., + * new_rate = (7/8) * old_rate + (1/8) * bw + */ + do_div(bw, 8); + if (bw == 0) + return 0; + bfqd->peak_rate *= 7; + do_div(bfqd->peak_rate, 8); + bfqd->peak_rate += bw; + update = 1; + bfq_log(bfqd, "new peak_rate=%llu", bfqd->peak_rate); + } + + update |= bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES - 1; + + if (bfqd->peak_rate_samples < BFQ_PEAK_RATE_SAMPLES) + bfqd->peak_rate_samples++; + + if (bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES && + update) { + int dev_type = blk_queue_nonrot(bfqd->queue); + if (bfqd->bfq_user_max_budget == 0) { + bfqd->bfq_max_budget = + bfq_calc_max_budget(bfqd->peak_rate, + timeout); + bfq_log(bfqd, "new max_budget=%lu", + bfqd->bfq_max_budget); + } + if (bfqd->device_speed == BFQ_BFQD_FAST && + bfqd->peak_rate < device_speed_thresh[dev_type]) { + bfqd->device_speed = BFQ_BFQD_SLOW; + bfqd->RT_prod = R_slow[dev_type] * + T_slow[dev_type]; + } else if (bfqd->device_speed == BFQ_BFQD_SLOW && + bfqd->peak_rate > device_speed_thresh[dev_type]) { + bfqd->device_speed = BFQ_BFQD_FAST; + bfqd->RT_prod = R_fast[dev_type] * + T_fast[dev_type]; + } + } + } + + /* + * If the process has been served for a too short time + * interval to let its possible sequential accesses prevail on + * the initial seek time needed to move the disk head on the + * first sector it requested, then give the process a chance + * and for the moment return false. + */ + if (bfqq->entity.budget <= bfq_max_budget(bfqd) / 8) + return 0; + + /* + * A process is considered ``slow'' (i.e., seeky, so that we + * cannot treat it fairly in the service domain, as it would + * slow down too much the other processes) if, when a slice + * ends for whatever reason, it has received service at a + * rate that would not be high enough to complete the budget + * before the budget timeout expiration. + */ + expected = bw * 1000 * timeout >> BFQ_RATE_SHIFT; + + /* + * Caveat: processes doing IO in the slower disk zones will + * tend to be slow(er) even if not seeky. And the estimated + * peak rate will actually be an average over the disk + * surface. Hence, to not be too harsh with unlucky processes, + * we keep a budget/3 margin of safety before declaring a + * process slow. + */ + return expected > (4 * bfqq->entity.budget) / 3; +} + +/* + * To be deemed as soft real-time, an application must meet two + * requirements. First, the application must not require an average + * bandwidth higher than the approximate bandwidth required to playback or + * record a compressed high-definition video. + * The next function is invoked on the completion of the last request of a + * batch, to compute the next-start time instant, soft_rt_next_start, such + * that, if the next request of the application does not arrive before + * soft_rt_next_start, then the above requirement on the bandwidth is met. + * + * The second requirement is that the request pattern of the application is + * isochronous, i.e., that, after issuing a request or a batch of requests, + * the application stops issuing new requests until all its pending requests + * have been completed. After that, the application may issue a new batch, + * and so on. + * For this reason the next function is invoked to compute + * soft_rt_next_start only for applications that meet this requirement, + * whereas soft_rt_next_start is set to infinity for applications that do + * not. + * + * Unfortunately, even a greedy application may happen to behave in an + * isochronous way if the CPU load is high. In fact, the application may + * stop issuing requests while the CPUs are busy serving other processes, + * then restart, then stop again for a while, and so on. In addition, if + * the disk achieves a low enough throughput with the request pattern + * issued by the application (e.g., because the request pattern is random + * and/or the device is slow), then the application may meet the above + * bandwidth requirement too. To prevent such a greedy application to be + * deemed as soft real-time, a further rule is used in the computation of + * soft_rt_next_start: soft_rt_next_start must be higher than the current + * time plus the maximum time for which the arrival of a request is waited + * for when a sync queue becomes idle, namely bfqd->bfq_slice_idle. + * This filters out greedy applications, as the latter issue instead their + * next request as soon as possible after the last one has been completed + * (in contrast, when a batch of requests is completed, a soft real-time + * application spends some time processing data). + * + * Unfortunately, the last filter may easily generate false positives if + * only bfqd->bfq_slice_idle is used as a reference time interval and one + * or both the following cases occur: + * 1) HZ is so low that the duration of a jiffy is comparable to or higher + * than bfqd->bfq_slice_idle. This happens, e.g., on slow devices with + * HZ=100. + * 2) jiffies, instead of increasing at a constant rate, may stop increasing + * for a while, then suddenly 'jump' by several units to recover the lost + * increments. This seems to happen, e.g., inside virtual machines. + * To address this issue, we do not use as a reference time interval just + * bfqd->bfq_slice_idle, but bfqd->bfq_slice_idle plus a few jiffies. In + * particular we add the minimum number of jiffies for which the filter + * seems to be quite precise also in embedded systems and KVM/QEMU virtual + * machines. + */ +static inline unsigned long bfq_bfqq_softrt_next_start(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + return max(bfqq->last_idle_bklogged + + HZ * bfqq->service_from_backlogged / + bfqd->bfq_wr_max_softrt_rate, + jiffies + bfqq->bfqd->bfq_slice_idle + 4); +} + +/* + * Return the largest-possible time instant such that, for as long as possible, + * the current time will be lower than this time instant according to the macro + * time_is_before_jiffies(). + */ +static inline unsigned long bfq_infinity_from_now(unsigned long now) +{ + return now + ULONG_MAX / 2; +} + +/** + * bfq_bfqq_expire - expire a queue. + * @bfqd: device owning the queue. + * @bfqq: the queue to expire. + * @compensate: if true, compensate for the time spent idling. + * @reason: the reason causing the expiration. + * + * + * If the process associated to the queue is slow (i.e., seeky), or in + * case of budget timeout, or, finally, if it is async, we + * artificially charge it an entire budget (independently of the + * actual service it received). As a consequence, the queue will get + * higher timestamps than the correct ones upon reactivation, and + * hence it will be rescheduled as if it had received more service + * than what it actually received. In the end, this class of processes + * will receive less service in proportion to how slowly they consume + * their budgets (and hence how seriously they tend to lower the + * throughput). + * + * In contrast, when a queue expires because it has been idling for + * too much or because it exhausted its budget, we do not touch the + * amount of service it has received. Hence when the queue will be + * reactivated and its timestamps updated, the latter will be in sync + * with the actual service received by the queue until expiration. + * + * Charging a full budget to the first type of queues and the exact + * service to the others has the effect of using the WF2Q+ policy to + * schedule the former on a timeslice basis, without violating the + * service domain guarantees of the latter. + */ +static void bfq_bfqq_expire(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + int compensate, + enum bfqq_expiration reason) +{ + int slow; + BUG_ON(bfqq != bfqd->in_service_queue); + + /* Update disk peak rate for autotuning and check whether the + * process is slow (see bfq_update_peak_rate). + */ + slow = bfq_update_peak_rate(bfqd, bfqq, compensate, reason); + + /* + * As above explained, 'punish' slow (i.e., seeky), timed-out + * and async queues, to favor sequential sync workloads. + * + * Processes doing I/O in the slower disk zones will tend to be + * slow(er) even if not seeky. Hence, since the estimated peak + * rate is actually an average over the disk surface, these + * processes may timeout just for bad luck. To avoid punishing + * them we do not charge a full budget to a process that + * succeeded in consuming at least 2/3 of its budget. + */ + if (slow || (reason == BFQ_BFQQ_BUDGET_TIMEOUT && + bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3)) + bfq_bfqq_charge_full_budget(bfqq); + + bfqq->service_from_backlogged += bfqq->entity.service; + + if (BFQQ_SEEKY(bfqq) && reason == BFQ_BFQQ_BUDGET_TIMEOUT && + !bfq_bfqq_constantly_seeky(bfqq)) { + bfq_mark_bfqq_constantly_seeky(bfqq); + if (!blk_queue_nonrot(bfqd->queue)) + bfqd->const_seeky_busy_in_flight_queues++; + } + + if (reason == BFQ_BFQQ_TOO_IDLE && + bfqq->entity.service <= 2 * bfqq->entity.budget / 10 ) + bfq_clear_bfqq_IO_bound(bfqq); + + if (bfqd->low_latency && bfqq->wr_coeff == 1) + bfqq->last_wr_start_finish = jiffies; + + if (bfqd->low_latency && bfqd->bfq_wr_max_softrt_rate > 0 && + RB_EMPTY_ROOT(&bfqq->sort_list)) { + /* + * If we get here, and there are no outstanding requests, + * then the request pattern is isochronous (see the comments + * to the function bfq_bfqq_softrt_next_start()). Hence we + * can compute soft_rt_next_start. If, instead, the queue + * still has outstanding requests, then we have to wait + * for the completion of all the outstanding requests to + * discover whether the request pattern is actually + * isochronous. + */ + if (bfqq->dispatched == 0) + bfqq->soft_rt_next_start = + bfq_bfqq_softrt_next_start(bfqd, bfqq); + else { + /* + * The application is still waiting for the + * completion of one or more requests: + * prevent it from possibly being incorrectly + * deemed as soft real-time by setting its + * soft_rt_next_start to infinity. In fact, + * without this assignment, the application + * would be incorrectly deemed as soft + * real-time if: + * 1) it issued a new request before the + * completion of all its in-flight + * requests, and + * 2) at that time, its soft_rt_next_start + * happened to be in the past. + */ + bfqq->soft_rt_next_start = + bfq_infinity_from_now(jiffies); + /* + * Schedule an update of soft_rt_next_start to when + * the task may be discovered to be isochronous. + */ + bfq_mark_bfqq_softrt_update(bfqq); + } + } + + bfq_log_bfqq(bfqd, bfqq, + "expire (%d, slow %d, num_disp %d, idle_win %d)", reason, + slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq)); + + /* + * Increase, decrease or leave budget unchanged according to + * reason. + */ + __bfq_bfqq_recalc_budget(bfqd, bfqq, reason); + __bfq_bfqq_expire(bfqd, bfqq); +} + +/* + * Budget timeout is not implemented through a dedicated timer, but + * just checked on request arrivals and completions, as well as on + * idle timer expirations. + */ +static int bfq_bfqq_budget_timeout(struct bfq_queue *bfqq) +{ + if (bfq_bfqq_budget_new(bfqq) || + time_before(jiffies, bfqq->budget_timeout)) + return 0; + return 1; +} + +/* + * If we expire a queue that is waiting for the arrival of a new + * request, we may prevent the fictitious timestamp back-shifting that + * allows the guarantees of the queue to be preserved (see [1] for + * this tricky aspect). Hence we return true only if this condition + * does not hold, or if the queue is slow enough to deserve only to be + * kicked off for preserving a high throughput. +*/ +static inline int bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq) +{ + bfq_log_bfqq(bfqq->bfqd, bfqq, + "may_budget_timeout: wait_request %d left %d timeout %d", + bfq_bfqq_wait_request(bfqq), + bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3, + bfq_bfqq_budget_timeout(bfqq)); + + return (!bfq_bfqq_wait_request(bfqq) || + bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3) + && + bfq_bfqq_budget_timeout(bfqq); +} + +/* + * Device idling is allowed only for the queues for which this function + * returns true. For this reason, the return value of this function plays a + * critical role for both throughput boosting and service guarantees. The + * return value is computed through a logical expression. In this rather + * long comment, we try to briefly describe all the details and motivations + * behind the components of this logical expression. + * + * First, the expression is false if bfqq is not sync, or if: bfqq happened + * to become active during a large burst of queue activations, and the + * pattern of requests bfqq contains boosts the throughput if bfqq is + * expired. In fact, queues that became active during a large burst benefit + * only from throughput, as discussed in the comments to bfq_handle_burst. + * In this respect, expiring bfqq certainly boosts the throughput on NCQ- + * capable flash-based devices, whereas, on rotational devices, it boosts + * the throughput only if bfqq contains random requests. + * + * On the opposite end, if (a) bfqq is sync, (b) the above burst-related + * condition does not hold, and (c) bfqq is being weight-raised, then the + * expression always evaluates to true, as device idling is instrumental + * for preserving low-latency guarantees (see [1]). If, instead, conditions + * (a) and (b) do hold, but (c) does not, then the expression evaluates to + * true only if: (1) bfqq is I/O-bound and has a non-null idle window, and + * (2) at least one of the following two conditions holds. + * The first condition is that the device is not performing NCQ, because + * idling the device most certainly boosts the throughput if this condition + * holds and bfqq is I/O-bound and has been granted a non-null idle window. + * The second compound condition is made of the logical AND of two components. + * + * The first component is true only if there is no weight-raised busy + * queue. This guarantees that the device is not idled for a sync non- + * weight-raised queue when there are busy weight-raised queues. The former + * is then expired immediately if empty. Combined with the timestamping + * rules of BFQ (see [1] for details), this causes sync non-weight-raised + * queues to get a lower number of requests served, and hence to ask for a + * lower number of requests from the request pool, before the busy weight- + * raised queues get served again. + * + * This is beneficial for the processes associated with weight-raised + * queues, when the request pool is saturated (e.g., in the presence of + * write hogs). In fact, if the processes associated with the other queues + * ask for requests at a lower rate, then weight-raised processes have a + * higher probability to get a request from the pool immediately (or at + * least soon) when they need one. Hence they have a higher probability to + * actually get a fraction of the disk throughput proportional to their + * high weight. This is especially true with NCQ-capable drives, which + * enqueue several requests in advance and further reorder internally- + * queued requests. + * + * In the end, mistreating non-weight-raised queues when there are busy + * weight-raised queues seems to mitigate starvation problems in the + * presence of heavy write workloads and NCQ, and hence to guarantee a + * higher application and system responsiveness in these hostile scenarios. + * + * If the first component of the compound condition is instead true, i.e., + * there is no weight-raised busy queue, then the second component of the + * compound condition takes into account service-guarantee and throughput + * issues related to NCQ (recall that the compound condition is evaluated + * only if the device is detected as supporting NCQ). + * + * As for service guarantees, allowing the drive to enqueue more than one + * request at a time, and hence delegating de facto final scheduling + * decisions to the drive's internal scheduler, causes loss of control on + * the actual request service order. In this respect, when the drive is + * allowed to enqueue more than one request at a time, the service + * distribution enforced by the drive's internal scheduler is likely to + * coincide with the desired device-throughput distribution only in the + * following, perfectly symmetric, scenario: + * 1) all active queues have the same weight, + * 2) all active groups at the same level in the groups tree have the same + * weight, + * 3) all active groups at the same level in the groups tree have the same + * number of children. + * + * Even in such a scenario, sequential I/O may still receive a preferential + * treatment, but this is not likely to be a big issue with flash-based + * devices, because of their non-dramatic loss of throughput with random + * I/O. Things do differ with HDDs, for which additional care is taken, as + * explained after completing the discussion for flash-based devices. + * + * Unfortunately, keeping the necessary state for evaluating exactly the + * above symmetry conditions would be quite complex and time-consuming. + * Therefore BFQ evaluates instead the following stronger sub-conditions, + * for which it is much easier to maintain the needed state: + * 1) all active queues have the same weight, + * 2) all active groups have the same weight, + * 3) all active groups have at most one active child each. + * In particular, the last two conditions are always true if hierarchical + * support and the cgroups interface are not enabled, hence no state needs + * to be maintained in this case. + * + * According to the above considerations, the second component of the + * compound condition evaluates to true if any of the above symmetry + * sub-condition does not hold, or the device is not flash-based. Therefore, + * if also the first component is true, then idling is allowed for a sync + * queue. These are the only sub-conditions considered if the device is + * flash-based, as, for such a device, it is sensible to force idling only + * for service-guarantee issues. In fact, as for throughput, idling + * NCQ-capable flash-based devices would not boost the throughput even + * with sequential I/O; rather it would lower the throughput in proportion + * to how fast the device is. In the end, (only) if all the three + * sub-conditions hold and the device is flash-based, the compound + * condition evaluates to false and therefore no idling is performed. + * + * As already said, things change with a rotational device, where idling + * boosts the throughput with sequential I/O (even with NCQ). Hence, for + * such a device the second component of the compound condition evaluates + * to true also if the following additional sub-condition does not hold: + * the queue is constantly seeky. Unfortunately, this different behavior + * with respect to flash-based devices causes an additional asymmetry: if + * some sync queues enjoy idling and some other sync queues do not, then + * the latter get a low share of the device throughput, simply because the + * former get many requests served after being set as in service, whereas + * the latter do not. As a consequence, to guarantee the desired throughput + * distribution, on HDDs the compound expression evaluates to true (and + * hence device idling is performed) also if the following last symmetry + * condition does not hold: no other queue is benefiting from idling. Also + * this last condition is actually replaced with a simpler-to-maintain and + * stronger condition: there is no busy queue which is not constantly seeky + * (and hence may also benefit from idling). + * + * To sum up, when all the required symmetry and throughput-boosting + * sub-conditions hold, the second component of the compound condition + * evaluates to false, and hence no idling is performed. This helps to + * keep the drives' internal queues full on NCQ-capable devices, and hence + * to boost the throughput, without causing 'almost' any loss of service + * guarantees. The 'almost' follows from the fact that, if the internal + * queue of one such device is filled while all the sub-conditions hold, + * but at some point in time some sub-condition stops to hold, then it may + * become impossible to let requests be served in the new desired order + * until all the requests already queued in the device have been served. + */ +static inline bool bfq_bfqq_must_not_expire(struct bfq_queue *bfqq) +{ + struct bfq_data *bfqd = bfqq->bfqd; +#ifdef CONFIG_CGROUP_BFQIO +#define symmetric_scenario (!bfqd->active_numerous_groups && \ + !bfq_differentiated_weights(bfqd)) +#else +#define symmetric_scenario (!bfq_differentiated_weights(bfqd)) +#endif +#define cond_for_seeky_on_ncq_hdd (bfq_bfqq_constantly_seeky(bfqq) && \ + bfqd->busy_in_flight_queues == \ + bfqd->const_seeky_busy_in_flight_queues) + +#define cond_for_expiring_in_burst (bfq_bfqq_in_large_burst(bfqq) && \ + bfqd->hw_tag && \ + (blk_queue_nonrot(bfqd->queue) || \ + bfq_bfqq_constantly_seeky(bfqq))) + +/* + * Condition for expiring a non-weight-raised queue (and hence not idling + * the device). + */ +#define cond_for_expiring_non_wr (bfqd->hw_tag && \ + (bfqd->wr_busy_queues > 0 || \ + (symmetric_scenario && \ + (blk_queue_nonrot(bfqd->queue) || \ + cond_for_seeky_on_ncq_hdd)))) + + return bfq_bfqq_sync(bfqq) && + !cond_for_expiring_in_burst && + (bfqq->wr_coeff > 1 || + (bfq_bfqq_IO_bound(bfqq) && bfq_bfqq_idle_window(bfqq) && + !cond_for_expiring_non_wr) + ); +} + +/* + * If the in-service queue is empty but sync, and the function + * bfq_bfqq_must_not_expire returns true, then: + * 1) the queue must remain in service and cannot be expired, and + * 2) the disk must be idled to wait for the possible arrival of a new + * request for the queue. + * See the comments to the function bfq_bfqq_must_not_expire for the reasons + * why performing device idling is the best choice to boost the throughput + * and preserve service guarantees when bfq_bfqq_must_not_expire itself + * returns true. + */ +static inline bool bfq_bfqq_must_idle(struct bfq_queue *bfqq) +{ + struct bfq_data *bfqd = bfqq->bfqd; + + return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 && + bfq_bfqq_must_not_expire(bfqq); +} + +/* + * Select a queue for service. If we have a current queue in service, + * check whether to continue servicing it, or retrieve and set a new one. + */ +static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq; + struct request *next_rq; + enum bfqq_expiration reason = BFQ_BFQQ_BUDGET_TIMEOUT; + + bfqq = bfqd->in_service_queue; + if (bfqq == NULL) + goto new_queue; + + bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue"); + + if (bfq_may_expire_for_budg_timeout(bfqq) && + !timer_pending(&bfqd->idle_slice_timer) && + !bfq_bfqq_must_idle(bfqq)) + goto expire; + + next_rq = bfqq->next_rq; + /* + * If bfqq has requests queued and it has enough budget left to + * serve them, keep the queue, otherwise expire it. + */ + if (next_rq != NULL) { + if (bfq_serv_to_charge(next_rq, bfqq) > + bfq_bfqq_budget_left(bfqq)) { + reason = BFQ_BFQQ_BUDGET_EXHAUSTED; + goto expire; + } else { + /* + * The idle timer may be pending because we may + * not disable disk idling even when a new request + * arrives. + */ + if (timer_pending(&bfqd->idle_slice_timer)) { + /* + * If we get here: 1) at least a new request + * has arrived but we have not disabled the + * timer because the request was too small, + * 2) then the block layer has unplugged + * the device, causing the dispatch to be + * invoked. + * + * Since the device is unplugged, now the + * requests are probably large enough to + * provide a reasonable throughput. + * So we disable idling. + */ + bfq_clear_bfqq_wait_request(bfqq); + del_timer(&bfqd->idle_slice_timer); + } + goto keep_queue; + } + } + + /* + * No requests pending. If the in-service queue still has requests + * in flight (possibly waiting for a completion) or is idling for a + * new request, then keep it. + */ + if (timer_pending(&bfqd->idle_slice_timer) || + (bfqq->dispatched != 0 && bfq_bfqq_must_not_expire(bfqq))) { + bfqq = NULL; + goto keep_queue; + } + + reason = BFQ_BFQQ_NO_MORE_REQUESTS; +expire: + bfq_bfqq_expire(bfqd, bfqq, 0, reason); +new_queue: + bfqq = bfq_set_in_service_queue(bfqd); + bfq_log(bfqd, "select_queue: new queue %d returned", + bfqq != NULL ? bfqq->pid : 0); +keep_queue: + return bfqq; +} + +static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + if (bfqq->wr_coeff > 1) { /* queue is being weight-raised */ + bfq_log_bfqq(bfqd, bfqq, + "raising period dur %u/%u msec, old coeff %u, w %d(%d)", + jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish), + jiffies_to_msecs(bfqq->wr_cur_max_time), + bfqq->wr_coeff, + bfqq->entity.weight, bfqq->entity.orig_weight); + + BUG_ON(bfqq != bfqd->in_service_queue && entity->weight != + entity->orig_weight * bfqq->wr_coeff); + if (entity->ioprio_changed) + bfq_log_bfqq(bfqd, bfqq, "WARN: pending prio change"); + + /* + * If the queue was activated in a burst, or + * too much time has elapsed from the beginning + * of this weight-raising period, or the queue has + * exceeded the acceptable number of cooperations, + * then end weight raising. + */ + if (bfq_bfqq_in_large_burst(bfqq) || + bfq_bfqq_cooperations(bfqq) >= bfqd->bfq_coop_thresh || + time_is_before_jiffies(bfqq->last_wr_start_finish + + bfqq->wr_cur_max_time)) { + bfqq->last_wr_start_finish = jiffies; + bfq_log_bfqq(bfqd, bfqq, + "wrais ending at %lu, rais_max_time %u", + bfqq->last_wr_start_finish, + jiffies_to_msecs(bfqq->wr_cur_max_time)); + bfq_bfqq_end_wr(bfqq); + } + } + /* Update weight both if it must be raised and if it must be lowered */ + if ((entity->weight > entity->orig_weight) != (bfqq->wr_coeff > 1)) + __bfq_entity_update_weight_prio( + bfq_entity_service_tree(entity), + entity); +} + +/* + * Dispatch one request from bfqq, moving it to the request queue + * dispatch list. + */ +static int bfq_dispatch_request(struct bfq_data *bfqd, + struct bfq_queue *bfqq) +{ + int dispatched = 0; + struct request *rq; + unsigned long service_to_charge; + + BUG_ON(RB_EMPTY_ROOT(&bfqq->sort_list)); + + /* Follow expired path, else get first next available. */ + rq = bfq_check_fifo(bfqq); + if (rq == NULL) + rq = bfqq->next_rq; + service_to_charge = bfq_serv_to_charge(rq, bfqq); + + if (service_to_charge > bfq_bfqq_budget_left(bfqq)) { + /* + * This may happen if the next rq is chosen in fifo order + * instead of sector order. The budget is properly + * dimensioned to be always sufficient to serve the next + * request only if it is chosen in sector order. The reason + * is that it would be quite inefficient and little useful + * to always make sure that the budget is large enough to + * serve even the possible next rq in fifo order. + * In fact, requests are seldom served in fifo order. + * + * Expire the queue for budget exhaustion, and make sure + * that the next act_budget is enough to serve the next + * request, even if it comes from the fifo expired path. + */ + bfqq->next_rq = rq; + /* + * Since this dispatch is failed, make sure that + * a new one will be performed + */ + if (!bfqd->rq_in_driver) + bfq_schedule_dispatch(bfqd); + goto expire; + } + + /* Finally, insert request into driver dispatch list. */ + bfq_bfqq_served(bfqq, service_to_charge); + bfq_dispatch_insert(bfqd->queue, rq); + + bfq_update_wr_data(bfqd, bfqq); + + bfq_log_bfqq(bfqd, bfqq, + "dispatched %u sec req (%llu), budg left %lu", + blk_rq_sectors(rq), + (long long unsigned)blk_rq_pos(rq), + bfq_bfqq_budget_left(bfqq)); + + dispatched++; + + if (bfqd->in_service_bic == NULL) { + atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount); + bfqd->in_service_bic = RQ_BIC(rq); + } + + if (bfqd->busy_queues > 1 && ((!bfq_bfqq_sync(bfqq) && + dispatched >= bfqd->bfq_max_budget_async_rq) || + bfq_class_idle(bfqq))) + goto expire; + + return dispatched; + +expire: + bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_EXHAUSTED); + return dispatched; +} + +static int __bfq_forced_dispatch_bfqq(struct bfq_queue *bfqq) +{ + int dispatched = 0; + + while (bfqq->next_rq != NULL) { + bfq_dispatch_insert(bfqq->bfqd->queue, bfqq->next_rq); + dispatched++; + } + + BUG_ON(!list_empty(&bfqq->fifo)); + return dispatched; +} + +/* + * Drain our current requests. + * Used for barriers and when switching io schedulers on-the-fly. + */ +static int bfq_forced_dispatch(struct bfq_data *bfqd) +{ + struct bfq_queue *bfqq, *n; + struct bfq_service_tree *st; + int dispatched = 0; + + bfqq = bfqd->in_service_queue; + if (bfqq != NULL) + __bfq_bfqq_expire(bfqd, bfqq); + + /* + * Loop through classes, and be careful to leave the scheduler + * in a consistent state, as feedback mechanisms and vtime + * updates cannot be disabled during the process. + */ + list_for_each_entry_safe(bfqq, n, &bfqd->active_list, bfqq_list) { + st = bfq_entity_service_tree(&bfqq->entity); + + dispatched += __bfq_forced_dispatch_bfqq(bfqq); + bfqq->max_budget = bfq_max_budget(bfqd); + + bfq_forget_idle(st); + } + + BUG_ON(bfqd->busy_queues != 0); + + return dispatched; +} + +static int bfq_dispatch_requests(struct request_queue *q, int force) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct bfq_queue *bfqq; + int max_dispatch; + + bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues); + if (bfqd->busy_queues == 0) + return 0; + + if (unlikely(force)) + return bfq_forced_dispatch(bfqd); + + bfqq = bfq_select_queue(bfqd); + if (bfqq == NULL) + return 0; + + max_dispatch = bfqd->bfq_quantum; + if (bfq_class_idle(bfqq)) + max_dispatch = 1; + + if (!bfq_bfqq_sync(bfqq)) + max_dispatch = bfqd->bfq_max_budget_async_rq; + + if (bfqq->dispatched >= max_dispatch) { + if (bfqd->busy_queues > 1) + return 0; + if (bfqq->dispatched >= 4 * max_dispatch) + return 0; + } + + if (bfqd->sync_flight != 0 && !bfq_bfqq_sync(bfqq)) + return 0; + + bfq_clear_bfqq_wait_request(bfqq); + BUG_ON(timer_pending(&bfqd->idle_slice_timer)); + + if (!bfq_dispatch_request(bfqd, bfqq)) + return 0; + + bfq_log_bfqq(bfqd, bfqq, "dispatched one request of %d (max_disp %d)", + bfqq->pid, max_dispatch); + + return 1; +} + +/* + * Task holds one reference to the queue, dropped when task exits. Each rq + * in-flight on this queue also holds a reference, dropped when rq is freed. + * + * Queue lock must be held here. + */ +static void bfq_put_queue(struct bfq_queue *bfqq) +{ + struct bfq_data *bfqd = bfqq->bfqd; + + BUG_ON(atomic_read(&bfqq->ref) <= 0); + + bfq_log_bfqq(bfqd, bfqq, "put_queue: %p %d", bfqq, + atomic_read(&bfqq->ref)); + if (!atomic_dec_and_test(&bfqq->ref)) + return; + + BUG_ON(rb_first(&bfqq->sort_list) != NULL); + BUG_ON(bfqq->allocated[READ] + bfqq->allocated[WRITE] != 0); + BUG_ON(bfqq->entity.tree != NULL); + BUG_ON(bfq_bfqq_busy(bfqq)); + BUG_ON(bfqd->in_service_queue == bfqq); + + if (bfq_bfqq_sync(bfqq)) + /* + * The fact that this queue is being destroyed does not + * invalidate the fact that this queue may have been + * activated during the current burst. As a consequence, + * although the queue does not exist anymore, and hence + * needs to be removed from the burst list if there, + * the burst size has not to be decremented. + */ + hlist_del_init(&bfqq->burst_list_node); + + bfq_log_bfqq(bfqd, bfqq, "put_queue: %p freed", bfqq); + + kmem_cache_free(bfq_pool, bfqq); +} + +static void bfq_put_cooperator(struct bfq_queue *bfqq) +{ + struct bfq_queue *__bfqq, *next; + + /* + * If this queue was scheduled to merge with another queue, be + * sure to drop the reference taken on that queue (and others in + * the merge chain). See bfq_setup_merge and bfq_merge_bfqqs. + */ + __bfqq = bfqq->new_bfqq; + while (__bfqq) { + if (__bfqq == bfqq) + break; + next = __bfqq->new_bfqq; + bfq_put_queue(__bfqq); + __bfqq = next; + } +} + +static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + if (bfqq == bfqd->in_service_queue) { + __bfq_bfqq_expire(bfqd, bfqq); + bfq_schedule_dispatch(bfqd); + } + + bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq, + atomic_read(&bfqq->ref)); + + bfq_put_cooperator(bfqq); + + bfq_put_queue(bfqq); +} + +static inline void bfq_init_icq(struct io_cq *icq) +{ + struct bfq_io_cq *bic = icq_to_bic(icq); + + bic->ttime.last_end_request = jiffies; + /* + * A newly created bic indicates that the process has just + * started doing I/O, and is probably mapping into memory its + * executable and libraries: it definitely needs weight raising. + * There is however the possibility that the process performs, + * for a while, I/O close to some other process. EQM intercepts + * this behavior and may merge the queue corresponding to the + * process with some other queue, BEFORE the weight of the queue + * is raised. Merged queues are not weight-raised (they are assumed + * to belong to processes that benefit only from high throughput). + * If the merge is basically the consequence of an accident, then + * the queue will be split soon and will get back its old weight. + * It is then important to write down somewhere that this queue + * does need weight raising, even if it did not make it to get its + * weight raised before being merged. To this purpose, we overload + * the field raising_time_left and assign 1 to it, to mark the queue + * as needing weight raising. + */ + bic->wr_time_left = 1; +} + +static void bfq_exit_icq(struct io_cq *icq) +{ + struct bfq_io_cq *bic = icq_to_bic(icq); + struct bfq_data *bfqd = bic_to_bfqd(bic); + + if (bic->bfqq[BLK_RW_ASYNC]) { + bfq_exit_bfqq(bfqd, bic->bfqq[BLK_RW_ASYNC]); + bic->bfqq[BLK_RW_ASYNC] = NULL; + } + + if (bic->bfqq[BLK_RW_SYNC]) { + /* + * If the bic is using a shared queue, put the reference + * taken on the io_context when the bic started using a + * shared bfq_queue. + */ + if (bfq_bfqq_coop(bic->bfqq[BLK_RW_SYNC])) + put_io_context(icq->ioc); + bfq_exit_bfqq(bfqd, bic->bfqq[BLK_RW_SYNC]); + bic->bfqq[BLK_RW_SYNC] = NULL; + } +} + +/* + * Update the entity prio values; note that the new values will not + * be used until the next (re)activation. + */ +static void bfq_init_prio_data(struct bfq_queue *bfqq, struct io_context *ioc) +{ + struct task_struct *tsk = current; + int ioprio_class; + + if (!bfq_bfqq_prio_changed(bfqq)) + return; + + ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); + switch (ioprio_class) { + default: + dev_err(bfqq->bfqd->queue->backing_dev_info.dev, + "bfq: bad prio class %d\n", ioprio_class); + case IOPRIO_CLASS_NONE: + /* + * No prio set, inherit CPU scheduling settings. + */ + bfqq->entity.new_ioprio = task_nice_ioprio(tsk); + bfqq->entity.new_ioprio_class = task_nice_ioclass(tsk); + break; + case IOPRIO_CLASS_RT: + bfqq->entity.new_ioprio = task_ioprio(ioc); + bfqq->entity.new_ioprio_class = IOPRIO_CLASS_RT; + break; + case IOPRIO_CLASS_BE: + bfqq->entity.new_ioprio = task_ioprio(ioc); + bfqq->entity.new_ioprio_class = IOPRIO_CLASS_BE; + break; + case IOPRIO_CLASS_IDLE: + bfqq->entity.new_ioprio_class = IOPRIO_CLASS_IDLE; + bfqq->entity.new_ioprio = 7; + bfq_clear_bfqq_idle_window(bfqq); + break; + } + + if (bfqq->entity.new_ioprio < 0 || + bfqq->entity.new_ioprio >= IOPRIO_BE_NR) { + printk(KERN_CRIT "bfq_init_prio_data: new_ioprio %d\n", + bfqq->entity.new_ioprio); + BUG(); + } + + bfqq->entity.ioprio_changed = 1; + + bfq_clear_bfqq_prio_changed(bfqq); +} + +static void bfq_changed_ioprio(struct io_context *ioc, + struct bfq_io_cq *bic) +{ + struct bfq_data *bfqd; + struct bfq_queue *bfqq, *new_bfqq; + struct bfq_group *bfqg; + unsigned long uninitialized_var(flags); + + bfqd = bfq_get_bfqd_locked(&(bic->icq.q->elevator->elevator_data), + &flags); + if (unlikely(bfqd == NULL)) + return; + + bfqq = bic->bfqq[BLK_RW_ASYNC]; + if (bfqq != NULL) { + bfqg = container_of(bfqq->entity.sched_data, struct bfq_group, + sched_data); + new_bfqq = bfq_get_queue(bfqd, bfqg, BLK_RW_ASYNC, bic->icq.ioc, + GFP_ATOMIC); + if (new_bfqq != NULL) { + bic->bfqq[BLK_RW_ASYNC] = new_bfqq; + bfq_log_bfqq(bfqd, bfqq, + "changed_ioprio: bfqq %p %d", + bfqq, atomic_read(&bfqq->ref)); + bfq_put_queue(bfqq); + } + } + + bfqq = bic->bfqq[BLK_RW_SYNC]; + if (bfqq != NULL) + bfq_mark_bfqq_prio_changed(bfqq); + + bfq_put_bfqd_unlock(bfqd, &flags); +} + +static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, + pid_t pid, int is_sync) +{ + RB_CLEAR_NODE(&bfqq->entity.rb_node); + INIT_LIST_HEAD(&bfqq->fifo); + INIT_HLIST_NODE(&bfqq->burst_list_node); + + atomic_set(&bfqq->ref, 0); + bfqq->bfqd = bfqd; + + bfq_mark_bfqq_prio_changed(bfqq); + + if (is_sync) { + if (!bfq_class_idle(bfqq)) + bfq_mark_bfqq_idle_window(bfqq); + bfq_mark_bfqq_sync(bfqq); + } + bfq_mark_bfqq_IO_bound(bfqq); + + /* Tentative initial value to trade off between thr and lat */ + bfqq->max_budget = (2 * bfq_max_budget(bfqd)) / 3; + bfqq->pid = pid; + + bfqq->wr_coeff = 1; + bfqq->last_wr_start_finish = 0; + /* + * Set to the value for which bfqq will not be deemed as + * soft rt when it becomes backlogged. + */ + bfqq->soft_rt_next_start = bfq_infinity_from_now(jiffies); +} + +static struct bfq_queue *bfq_find_alloc_queue(struct bfq_data *bfqd, + struct bfq_group *bfqg, + int is_sync, + struct io_context *ioc, + gfp_t gfp_mask) +{ + struct bfq_queue *bfqq, *new_bfqq = NULL; + struct bfq_io_cq *bic; + +retry: + bic = bfq_bic_lookup(bfqd, ioc); + /* bic always exists here */ + bfqq = bic_to_bfqq(bic, is_sync); + + /* + * Always try a new alloc if we fall back to the OOM bfqq + * originally, since it should just be a temporary situation. + */ + if (bfqq == NULL || bfqq == &bfqd->oom_bfqq) { + bfqq = NULL; + if (new_bfqq != NULL) { + bfqq = new_bfqq; + new_bfqq = NULL; + } else if (gfp_mask & __GFP_WAIT) { + spin_unlock_irq(bfqd->queue->queue_lock); + new_bfqq = kmem_cache_alloc_node(bfq_pool, + gfp_mask | __GFP_ZERO, + bfqd->queue->node); + spin_lock_irq(bfqd->queue->queue_lock); + if (new_bfqq != NULL) + goto retry; + } else { + bfqq = kmem_cache_alloc_node(bfq_pool, + gfp_mask | __GFP_ZERO, + bfqd->queue->node); + } + + if (bfqq != NULL) { + bfq_init_bfqq(bfqd, bfqq, current->pid, is_sync); + bfq_init_prio_data(bfqq, ioc); + bfq_init_entity(&bfqq->entity, bfqg); + bfq_log_bfqq(bfqd, bfqq, "allocated"); + } else { + bfqq = &bfqd->oom_bfqq; + bfq_log_bfqq(bfqd, bfqq, "using oom bfqq"); + } + } + + if (new_bfqq != NULL) + kmem_cache_free(bfq_pool, new_bfqq); + + return bfqq; +} + +static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd, + struct bfq_group *bfqg, + int ioprio_class, int ioprio) +{ + switch (ioprio_class) { + case IOPRIO_CLASS_RT: + return &bfqg->async_bfqq[0][ioprio]; + case IOPRIO_CLASS_BE: + return &bfqg->async_bfqq[1][ioprio]; + case IOPRIO_CLASS_IDLE: + return &bfqg->async_idle_bfqq; + default: + BUG(); + } +} + +static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, + struct bfq_group *bfqg, int is_sync, + struct io_context *ioc, gfp_t gfp_mask) +{ + const int ioprio = task_ioprio(ioc); + const int ioprio_class = task_ioprio_class(ioc); + struct bfq_queue **async_bfqq = NULL; + struct bfq_queue *bfqq = NULL; + + if (!is_sync) { + async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class, + ioprio); + bfqq = *async_bfqq; + } + + if (bfqq == NULL) + bfqq = bfq_find_alloc_queue(bfqd, bfqg, is_sync, ioc, gfp_mask); + + /* + * Pin the queue now that it's allocated, scheduler exit will + * prune it. + */ + if (!is_sync && *async_bfqq == NULL) { + atomic_inc(&bfqq->ref); + bfq_log_bfqq(bfqd, bfqq, "get_queue, bfqq not in async: %p, %d", + bfqq, atomic_read(&bfqq->ref)); + *async_bfqq = bfqq; + } + + atomic_inc(&bfqq->ref); + bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq, + atomic_read(&bfqq->ref)); + return bfqq; +} + +static void bfq_update_io_thinktime(struct bfq_data *bfqd, + struct bfq_io_cq *bic) +{ + unsigned long elapsed = jiffies - bic->ttime.last_end_request; + unsigned long ttime = min(elapsed, 2UL * bfqd->bfq_slice_idle); + + bic->ttime.ttime_samples = (7*bic->ttime.ttime_samples + 256) / 8; + bic->ttime.ttime_total = (7*bic->ttime.ttime_total + 256*ttime) / 8; + bic->ttime.ttime_mean = (bic->ttime.ttime_total + 128) / + bic->ttime.ttime_samples; +} + +static void bfq_update_io_seektime(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + struct request *rq) +{ + sector_t sdist; + u64 total; + + if (bfqq->last_request_pos < blk_rq_pos(rq)) + sdist = blk_rq_pos(rq) - bfqq->last_request_pos; + else + sdist = bfqq->last_request_pos - blk_rq_pos(rq); + + /* + * Don't allow the seek distance to get too large from the + * odd fragment, pagein, etc. + */ + if (bfqq->seek_samples == 0) /* first request, not really a seek */ + sdist = 0; + else if (bfqq->seek_samples <= 60) /* second & third seek */ + sdist = min(sdist, (bfqq->seek_mean * 4) + 2*1024*1024); + else + sdist = min(sdist, (bfqq->seek_mean * 4) + 2*1024*64); + + bfqq->seek_samples = (7*bfqq->seek_samples + 256) / 8; + bfqq->seek_total = (7*bfqq->seek_total + (u64)256*sdist) / 8; + total = bfqq->seek_total + (bfqq->seek_samples/2); + do_div(total, bfqq->seek_samples); + bfqq->seek_mean = (sector_t)total; + + bfq_log_bfqq(bfqd, bfqq, "dist=%llu mean=%llu", (u64)sdist, + (u64)bfqq->seek_mean); +} + +/* + * Disable idle window if the process thinks too long or seeks so much that + * it doesn't matter. + */ +static void bfq_update_idle_window(struct bfq_data *bfqd, + struct bfq_queue *bfqq, + struct bfq_io_cq *bic) +{ + int enable_idle; + + /* Don't idle for async or idle io prio class. */ + if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq)) + return; + + /* Idle window just restored, statistics are meaningless. */ + if (bfq_bfqq_just_split(bfqq)) + return; + + enable_idle = bfq_bfqq_idle_window(bfqq); + + if (atomic_read(&bic->icq.ioc->nr_tasks) == 0 || + bfqd->bfq_slice_idle == 0 || + (bfqd->hw_tag && BFQQ_SEEKY(bfqq) && + bfqq->wr_coeff == 1)) + enable_idle = 0; + else if (bfq_sample_valid(bic->ttime.ttime_samples)) { + if (bic->ttime.ttime_mean > bfqd->bfq_slice_idle && + bfqq->wr_coeff == 1) + enable_idle = 0; + else + enable_idle = 1; + } + bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d", + enable_idle); + + if (enable_idle) + bfq_mark_bfqq_idle_window(bfqq); + else + bfq_clear_bfqq_idle_window(bfqq); +} + +/* + * Called when a new fs request (rq) is added to bfqq. Check if there's + * something we should do about it. + */ +static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq, + struct request *rq) +{ + struct bfq_io_cq *bic = RQ_BIC(rq); + + if (rq->cmd_flags & REQ_META) + bfqq->meta_pending++; + + bfq_update_io_thinktime(bfqd, bic); + bfq_update_io_seektime(bfqd, bfqq, rq); + if (!BFQQ_SEEKY(bfqq) && bfq_bfqq_constantly_seeky(bfqq)) { + bfq_clear_bfqq_constantly_seeky(bfqq); + if (!blk_queue_nonrot(bfqd->queue)) { + BUG_ON(!bfqd->const_seeky_busy_in_flight_queues); + bfqd->const_seeky_busy_in_flight_queues--; + } + } + if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 || + !BFQQ_SEEKY(bfqq)) + bfq_update_idle_window(bfqd, bfqq, bic); + bfq_clear_bfqq_just_split(bfqq); + + bfq_log_bfqq(bfqd, bfqq, + "rq_enqueued: idle_window=%d (seeky %d, mean %llu)", + bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq), + (long long unsigned)bfqq->seek_mean); + + bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq); + + if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) { + int small_req = bfqq->queued[rq_is_sync(rq)] == 1 && + blk_rq_sectors(rq) < 32; + int budget_timeout = bfq_bfqq_budget_timeout(bfqq); + + /* + * There is just this request queued: if the request + * is small and the queue is not to be expired, then + * just exit. + * + * In this way, if the disk is being idled to wait for + * a new request from the in-service queue, we avoid + * unplugging the device and committing the disk to serve + * just a small request. On the contrary, we wait for + * the block layer to decide when to unplug the device: + * hopefully, new requests will be merged to this one + * quickly, then the device will be unplugged and + * larger requests will be dispatched. + */ + if (small_req && !budget_timeout) + return; + + /* + * A large enough request arrived, or the queue is to + * be expired: in both cases disk idling is to be + * stopped, so clear wait_request flag and reset + * timer. + */ + bfq_clear_bfqq_wait_request(bfqq); + del_timer(&bfqd->idle_slice_timer); + + /* + * The queue is not empty, because a new request just + * arrived. Hence we can safely expire the queue, in + * case of budget timeout, without risking that the + * timestamps of the queue are not updated correctly. + * See [1] for more details. + */ + if (budget_timeout) + bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_TIMEOUT); + + /* + * Let the request rip immediately, or let a new queue be + * selected if bfqq has just been expired. + */ + __blk_run_queue(bfqd->queue); + } +} + +static void bfq_insert_request(struct request_queue *q, struct request *rq) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct bfq_queue *bfqq = RQ_BFQQ(rq), *new_bfqq; + + assert_spin_locked(bfqd->queue->queue_lock); + + /* + * An unplug may trigger a requeue of a request from the device + * driver: make sure we are in process context while trying to + * merge two bfq_queues. + */ + if (!in_interrupt()) { + new_bfqq = bfq_setup_cooperator(bfqd, bfqq, rq, true); + if (new_bfqq != NULL) { + if (bic_to_bfqq(RQ_BIC(rq), 1) != bfqq) + new_bfqq = bic_to_bfqq(RQ_BIC(rq), 1); + /* + * Release the request's reference to the old bfqq + * and make sure one is taken to the shared queue. + */ + new_bfqq->allocated[rq_data_dir(rq)]++; + bfqq->allocated[rq_data_dir(rq)]--; + atomic_inc(&new_bfqq->ref); + bfq_put_queue(bfqq); + if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq) + bfq_merge_bfqqs(bfqd, RQ_BIC(rq), + bfqq, new_bfqq); + rq->elv.priv[1] = new_bfqq; + bfqq = new_bfqq; + } else + bfq_bfqq_increase_failed_cooperations(bfqq); + } + + bfq_init_prio_data(bfqq, RQ_BIC(rq)->icq.ioc); + + bfq_add_request(rq); + + /* + * Here a newly-created bfq_queue has already started a weight-raising + * period: clear raising_time_left to prevent bfq_bfqq_save_state() + * from assigning it a full weight-raising period. See the detailed + * comments about this field in bfq_init_icq(). + */ + if (bfqq->bic != NULL) + bfqq->bic->wr_time_left = 0; + rq_set_fifo_time(rq, jiffies + bfqd->bfq_fifo_expire[rq_is_sync(rq)]); + list_add_tail(&rq->queuelist, &bfqq->fifo); + + bfq_rq_enqueued(bfqd, bfqq, rq); +} + +static void bfq_update_hw_tag(struct bfq_data *bfqd) +{ + bfqd->max_rq_in_driver = max(bfqd->max_rq_in_driver, + bfqd->rq_in_driver); + + if (bfqd->hw_tag == 1) + return; + + /* + * This sample is valid if the number of outstanding requests + * is large enough to allow a queueing behavior. Note that the + * sum is not exact, as it's not taking into account deactivated + * requests. + */ + if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD) + return; + + if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES) + return; + + bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD; + bfqd->max_rq_in_driver = 0; + bfqd->hw_tag_samples = 0; +} + +static void bfq_completed_request(struct request_queue *q, struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + struct bfq_data *bfqd = bfqq->bfqd; + bool sync = bfq_bfqq_sync(bfqq); + + bfq_log_bfqq(bfqd, bfqq, "completed one req with %u sects left (%d)", + blk_rq_sectors(rq), sync); + + bfq_update_hw_tag(bfqd); + + BUG_ON(!bfqd->rq_in_driver); + BUG_ON(!bfqq->dispatched); + bfqd->rq_in_driver--; + bfqq->dispatched--; + + if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) { + bfq_weights_tree_remove(bfqd, &bfqq->entity, + &bfqd->queue_weights_tree); + if (!blk_queue_nonrot(bfqd->queue)) { + BUG_ON(!bfqd->busy_in_flight_queues); + bfqd->busy_in_flight_queues--; + if (bfq_bfqq_constantly_seeky(bfqq)) { + BUG_ON(!bfqd-> + const_seeky_busy_in_flight_queues); + bfqd->const_seeky_busy_in_flight_queues--; + } + } + } + + if (sync) { + bfqd->sync_flight--; + RQ_BIC(rq)->ttime.last_end_request = jiffies; + } + + /* + * If we are waiting to discover whether the request pattern of the + * task associated with the queue is actually isochronous, and + * both requisites for this condition to hold are satisfied, then + * compute soft_rt_next_start (see the comments to the function + * bfq_bfqq_softrt_next_start()). + */ + if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 && + RB_EMPTY_ROOT(&bfqq->sort_list)) + bfqq->soft_rt_next_start = + bfq_bfqq_softrt_next_start(bfqd, bfqq); + + /* + * If this is the in-service queue, check if it needs to be expired, + * or if we want to idle in case it has no pending requests. + */ + if (bfqd->in_service_queue == bfqq) { + if (bfq_bfqq_budget_new(bfqq)) + bfq_set_budget_timeout(bfqd); + + if (bfq_bfqq_must_idle(bfqq)) { + bfq_arm_slice_timer(bfqd); + goto out; + } else if (bfq_may_expire_for_budg_timeout(bfqq)) + bfq_bfqq_expire(bfqd, bfqq, 0, BFQ_BFQQ_BUDGET_TIMEOUT); + else if (RB_EMPTY_ROOT(&bfqq->sort_list) && + (bfqq->dispatched == 0 || + !bfq_bfqq_must_not_expire(bfqq))) + bfq_bfqq_expire(bfqd, bfqq, 0, + BFQ_BFQQ_NO_MORE_REQUESTS); + } + + if (!bfqd->rq_in_driver) + bfq_schedule_dispatch(bfqd); + +out: + return; +} + +static inline int __bfq_may_queue(struct bfq_queue *bfqq) +{ + if (bfq_bfqq_wait_request(bfqq) && bfq_bfqq_must_alloc(bfqq)) { + bfq_clear_bfqq_must_alloc(bfqq); + return ELV_MQUEUE_MUST; + } + + return ELV_MQUEUE_MAY; +} + +static int bfq_may_queue(struct request_queue *q, int rw) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct task_struct *tsk = current; + struct bfq_io_cq *bic; + struct bfq_queue *bfqq; + + /* + * Don't force setup of a queue from here, as a call to may_queue + * does not necessarily imply that a request actually will be + * queued. So just lookup a possibly existing queue, or return + * 'may queue' if that fails. + */ + bic = bfq_bic_lookup(bfqd, tsk->io_context); + if (bic == NULL) + return ELV_MQUEUE_MAY; + + bfqq = bic_to_bfqq(bic, rw_is_sync(rw)); + if (bfqq != NULL) { + bfq_init_prio_data(bfqq, bic->icq.ioc); + + return __bfq_may_queue(bfqq); + } + + return ELV_MQUEUE_MAY; +} + +/* + * Queue lock held here. + */ +static void bfq_put_request(struct request *rq) +{ + struct bfq_queue *bfqq = RQ_BFQQ(rq); + + if (bfqq != NULL) { + const int rw = rq_data_dir(rq); + + BUG_ON(!bfqq->allocated[rw]); + bfqq->allocated[rw]--; + + rq->elv.priv[0] = NULL; + rq->elv.priv[1] = NULL; + + bfq_log_bfqq(bfqq->bfqd, bfqq, "put_request %p, %d", + bfqq, atomic_read(&bfqq->ref)); + bfq_put_queue(bfqq); + } +} + +/* + * Returns NULL if a new bfqq should be allocated, or the old bfqq if this + * was the last process referring to said bfqq. + */ +static struct bfq_queue * +bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq) +{ + bfq_log_bfqq(bfqq->bfqd, bfqq, "splitting queue"); + + put_io_context(bic->icq.ioc); + + if (bfqq_process_refs(bfqq) == 1) { + bfqq->pid = current->pid; + bfq_clear_bfqq_coop(bfqq); + bfq_clear_bfqq_split_coop(bfqq); + return bfqq; + } + + bic_set_bfqq(bic, NULL, 1); + + bfq_put_cooperator(bfqq); + + bfq_put_queue(bfqq); + return NULL; +} + +/* + * Allocate bfq data structures associated with this request. + */ +static int bfq_set_request(struct request_queue *q, struct request *rq, + gfp_t gfp_mask) +{ + struct bfq_data *bfqd = q->elevator->elevator_data; + struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq); + const int rw = rq_data_dir(rq); + const int is_sync = rq_is_sync(rq); + struct bfq_queue *bfqq; + struct bfq_group *bfqg; + unsigned long flags; + bool split = false; + + /* handle changed prio notifications; cgroup change is handled separately */ + if (unlikely(icq_get_changed(&bic->icq) & ICQ_IOPRIO_CHANGED)) + bfq_changed_ioprio(bic->icq.ioc, bic); + + might_sleep_if(gfp_mask & __GFP_WAIT); + + spin_lock_irqsave(q->queue_lock, flags); + + if (bic == NULL) + goto queue_fail; + + bfqg = bfq_bic_update_cgroup(bic); + +new_queue: + bfqq = bic_to_bfqq(bic, is_sync); + if (bfqq == NULL || bfqq == &bfqd->oom_bfqq) { + bfqq = bfq_get_queue(bfqd, bfqg, is_sync, bic->icq.ioc, gfp_mask); + bic_set_bfqq(bic, bfqq, is_sync); + if (split && is_sync) { + if ((bic->was_in_burst_list && bfqd->large_burst) || + bic->saved_in_large_burst) + bfq_mark_bfqq_in_large_burst(bfqq); + else { + bfq_clear_bfqq_in_large_burst(bfqq); + if (bic->was_in_burst_list) + hlist_add_head(&bfqq->burst_list_node, + &bfqd->burst_list); + } + } + } else { + /* If the queue was seeky for too long, break it apart. */ + if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq)) { + bfq_log_bfqq(bfqd, bfqq, "breaking apart bfqq"); + bfqq = bfq_split_bfqq(bic, bfqq); + split = true; + if (!bfqq) + goto new_queue; + } + } + + bfqq->allocated[rw]++; + atomic_inc(&bfqq->ref); + bfq_log_bfqq(bfqd, bfqq, "set_request: bfqq %p, %d", bfqq, + atomic_read(&bfqq->ref)); + + rq->elv.priv[0] = bic; + rq->elv.priv[1] = bfqq; + + /* + * If a bfq_queue has only one process reference, it is owned + * by only one bfq_io_cq: we can set the bic field of the + * bfq_queue to the address of that structure. Also, if the + * queue has just been split, mark a flag so that the + * information is available to the other scheduler hooks. + */ + if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) { + bfqq->bic = bic; + if (split) { + bfq_mark_bfqq_just_split(bfqq); + /* + * If the queue has just been split from a shared + * queue, restore the idle window and the possible + * weight raising period. + */ + bfq_bfqq_resume_state(bfqq, bic); + } + } + + spin_unlock_irqrestore(q->queue_lock, flags); + + return 0; + +queue_fail: + bfq_schedule_dispatch(bfqd); + spin_unlock_irqrestore(q->queue_lock, flags); + + return 1; +} + +static void bfq_kick_queue(struct work_struct *work) +{ + struct bfq_data *bfqd = + container_of(work, struct bfq_data, unplug_work); + struct request_queue *q = bfqd->queue; + + spin_lock_irq(q->queue_lock); + __blk_run_queue(q); + spin_unlock_irq(q->queue_lock); +} + +/* + * Handler of the expiration of the timer running if the in-service queue + * is idling inside its time slice. + */ +static void bfq_idle_slice_timer(unsigned long data) +{ + struct bfq_data *bfqd = (struct bfq_data *)data; + struct bfq_queue *bfqq; + unsigned long flags; + enum bfqq_expiration reason; + + spin_lock_irqsave(bfqd->queue->queue_lock, flags); + + bfqq = bfqd->in_service_queue; + /* + * Theoretical race here: the in-service queue can be NULL or + * different from the queue that was idling if the timer handler + * spins on the queue_lock and a new request arrives for the + * current queue and there is a full dispatch cycle that changes + * the in-service queue. This can hardly happen, but in the worst + * case we just expire a queue too early. + */ + if (bfqq != NULL) { + bfq_log_bfqq(bfqd, bfqq, "slice_timer expired"); + if (bfq_bfqq_budget_timeout(bfqq)) + /* + * Also here the queue can be safely expired + * for budget timeout without wasting + * guarantees + */ + reason = BFQ_BFQQ_BUDGET_TIMEOUT; + else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0) + /* + * The queue may not be empty upon timer expiration, + * because we may not disable the timer when the + * first request of the in-service queue arrives + * during disk idling. + */ + reason = BFQ_BFQQ_TOO_IDLE; + else + goto schedule_dispatch; + + bfq_bfqq_expire(bfqd, bfqq, 1, reason); + } + +schedule_dispatch: + bfq_schedule_dispatch(bfqd); + + spin_unlock_irqrestore(bfqd->queue->queue_lock, flags); +} + +static void bfq_shutdown_timer_wq(struct bfq_data *bfqd) +{ + del_timer_sync(&bfqd->idle_slice_timer); + cancel_work_sync(&bfqd->unplug_work); +} + +static inline void __bfq_put_async_bfqq(struct bfq_data *bfqd, + struct bfq_queue **bfqq_ptr) +{ + struct bfq_group *root_group = bfqd->root_group; + struct bfq_queue *bfqq = *bfqq_ptr; + + bfq_log(bfqd, "put_async_bfqq: %p", bfqq); + if (bfqq != NULL) { + bfq_bfqq_move(bfqd, bfqq, &bfqq->entity, root_group); + bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d", + bfqq, atomic_read(&bfqq->ref)); + bfq_put_queue(bfqq); + *bfqq_ptr = NULL; + } +} + +/* + * Release all the bfqg references to its async queues. If we are + * deallocating the group these queues may still contain requests, so + * we reparent them to the root cgroup (i.e., the only one that will + * exist for sure until all the requests on a device are gone). + */ +static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg) +{ + int i, j; + + for (i = 0; i < 2; i++) + for (j = 0; j < IOPRIO_BE_NR; j++) + __bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]); + + __bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq); +} + +static void bfq_exit_queue(struct elevator_queue *e) +{ + struct bfq_data *bfqd = e->elevator_data; + struct request_queue *q = bfqd->queue; + struct bfq_queue *bfqq, *n; + + bfq_shutdown_timer_wq(bfqd); + + spin_lock_irq(q->queue_lock); + + BUG_ON(bfqd->in_service_queue != NULL); + list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list) + bfq_deactivate_bfqq(bfqd, bfqq, 0); + + bfq_disconnect_groups(bfqd); + spin_unlock_irq(q->queue_lock); + + bfq_shutdown_timer_wq(bfqd); + + synchronize_rcu(); + + BUG_ON(timer_pending(&bfqd->idle_slice_timer)); + + bfq_free_root_group(bfqd); + kfree(bfqd); +} + +static void *bfq_init_queue(struct request_queue *q) +{ + struct bfq_group *bfqg; + struct bfq_data *bfqd; + + bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node); + if (bfqd == NULL) + return NULL; + + /* + * Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues. + * Grab a permanent reference to it, so that the normal code flow + * will not attempt to free it. + */ + bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, 1, 0); + atomic_inc(&bfqd->oom_bfqq.ref); + bfqd->oom_bfqq.entity.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO; + bfqd->oom_bfqq.entity.new_ioprio_class = IOPRIO_CLASS_BE; + /* + * Trigger weight initialization, according to ioprio, at the + * oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio + * class won't be changed any more. + */ + bfqd->oom_bfqq.entity.ioprio_changed = 1; + + bfqd->queue = q; + + bfqg = bfq_alloc_root_group(bfqd, q->node); + if (bfqg == NULL) { + kfree(bfqd); + return NULL; + } + + bfqd->root_group = bfqg; + bfq_init_entity(&bfqd->oom_bfqq.entity, bfqd->root_group); +#ifdef CONFIG_CGROUP_BFQIO + bfqd->active_numerous_groups = 0; +#endif + + init_timer(&bfqd->idle_slice_timer); + bfqd->idle_slice_timer.function = bfq_idle_slice_timer; + bfqd->idle_slice_timer.data = (unsigned long)bfqd; + + bfqd->rq_pos_tree = RB_ROOT; + bfqd->queue_weights_tree = RB_ROOT; + bfqd->group_weights_tree = RB_ROOT; + + INIT_WORK(&bfqd->unplug_work, bfq_kick_queue); + + INIT_LIST_HEAD(&bfqd->active_list); + INIT_LIST_HEAD(&bfqd->idle_list); + INIT_HLIST_HEAD(&bfqd->burst_list); + + bfqd->hw_tag = -1; + + bfqd->bfq_max_budget = bfq_default_max_budget; + + bfqd->bfq_quantum = bfq_quantum; + bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0]; + bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1]; + bfqd->bfq_back_max = bfq_back_max; + bfqd->bfq_back_penalty = bfq_back_penalty; + bfqd->bfq_slice_idle = bfq_slice_idle; + bfqd->bfq_class_idle_last_service = 0; + bfqd->bfq_max_budget_async_rq = bfq_max_budget_async_rq; + bfqd->bfq_timeout[BLK_RW_ASYNC] = bfq_timeout_async; + bfqd->bfq_timeout[BLK_RW_SYNC] = bfq_timeout_sync; + + bfqd->bfq_coop_thresh = 2; + bfqd->bfq_failed_cooperations = 7000; + bfqd->bfq_requests_within_timer = 120; + + bfqd->bfq_large_burst_thresh = 11; + bfqd->bfq_burst_interval = msecs_to_jiffies(500); + + bfqd->low_latency = true; + + bfqd->bfq_wr_coeff = 20; + bfqd->bfq_wr_rt_max_time = msecs_to_jiffies(300); + bfqd->bfq_wr_max_time = 0; + bfqd->bfq_wr_min_idle_time = msecs_to_jiffies(2000); + bfqd->bfq_wr_min_inter_arr_async = msecs_to_jiffies(500); + bfqd->bfq_wr_max_softrt_rate = 7000; /* + * Approximate rate required + * to playback or record a + * high-definition compressed + * video. + */ + bfqd->wr_busy_queues = 0; + bfqd->busy_in_flight_queues = 0; + bfqd->const_seeky_busy_in_flight_queues = 0; + + /* + * Begin by assuming, optimistically, that the device peak rate is + * equal to the highest reference rate. + */ + bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] * + T_fast[blk_queue_nonrot(bfqd->queue)]; + bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)]; + bfqd->device_speed = BFQ_BFQD_FAST; + + return bfqd; +} + +static void bfq_slab_kill(void) +{ + if (bfq_pool != NULL) + kmem_cache_destroy(bfq_pool); +} + +static int __init bfq_slab_setup(void) +{ + bfq_pool = KMEM_CACHE(bfq_queue, 0); + if (bfq_pool == NULL) + return -ENOMEM; + return 0; +} + +static ssize_t bfq_var_show(unsigned int var, char *page) +{ + return sprintf(page, "%d\n", var); +} + +static ssize_t bfq_var_store(unsigned long *var, const char *page, + size_t count) +{ + unsigned long new_val; + int ret = kstrtoul(page, 10, &new_val); + + if (ret == 0) + *var = new_val; + + return count; +} + +static ssize_t bfq_wr_max_time_show(struct elevator_queue *e, char *page) +{ + struct bfq_data *bfqd = e->elevator_data; + return sprintf(page, "%d\n", bfqd->bfq_wr_max_time > 0 ? + jiffies_to_msecs(bfqd->bfq_wr_max_time) : + jiffies_to_msecs(bfq_wr_duration(bfqd))); +} + +static ssize_t bfq_weights_show(struct elevator_queue *e, char *page) +{ + struct bfq_queue *bfqq; + struct bfq_data *bfqd = e->elevator_data; + ssize_t num_char = 0; + + num_char += sprintf(page + num_char, "Tot reqs queued %d\n\n", + bfqd->queued); + + spin_lock_irq(bfqd->queue->queue_lock); + + num_char += sprintf(page + num_char, "Active:\n"); + list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) { + num_char += sprintf(page + num_char, + "pid%d: weight %hu, nr_queued %d %d, dur %d/%u\n", + bfqq->pid, + bfqq->entity.weight, + bfqq->queued[0], + bfqq->queued[1], + jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish), + jiffies_to_msecs(bfqq->wr_cur_max_time)); + } + + num_char += sprintf(page + num_char, "Idle:\n"); + list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list) { + num_char += sprintf(page + num_char, + "pid%d: weight %hu, dur %d/%u\n", + bfqq->pid, + bfqq->entity.weight, + jiffies_to_msecs(jiffies - + bfqq->last_wr_start_finish), + jiffies_to_msecs(bfqq->wr_cur_max_time)); + } + + spin_unlock_irq(bfqd->queue->queue_lock); + + return num_char; +} + +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct bfq_data *bfqd = e->elevator_data; \ + unsigned int __data = __VAR; \ + if (__CONV) \ + __data = jiffies_to_msecs(__data); \ + return bfq_var_show(__data, (page)); \ +} +SHOW_FUNCTION(bfq_quantum_show, bfqd->bfq_quantum, 0); +SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 1); +SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 1); +SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0); +SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0); +SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 1); +SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0); +SHOW_FUNCTION(bfq_max_budget_async_rq_show, + bfqd->bfq_max_budget_async_rq, 0); +SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout[BLK_RW_SYNC], 1); +SHOW_FUNCTION(bfq_timeout_async_show, bfqd->bfq_timeout[BLK_RW_ASYNC], 1); +SHOW_FUNCTION(bfq_low_latency_show, bfqd->low_latency, 0); +SHOW_FUNCTION(bfq_wr_coeff_show, bfqd->bfq_wr_coeff, 0); +SHOW_FUNCTION(bfq_wr_rt_max_time_show, bfqd->bfq_wr_rt_max_time, 1); +SHOW_FUNCTION(bfq_wr_min_idle_time_show, bfqd->bfq_wr_min_idle_time, 1); +SHOW_FUNCTION(bfq_wr_min_inter_arr_async_show, bfqd->bfq_wr_min_inter_arr_async, + 1); +SHOW_FUNCTION(bfq_wr_max_softrt_rate_show, bfqd->bfq_wr_max_softrt_rate, 0); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t \ +__FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct bfq_data *bfqd = e->elevator_data; \ + unsigned long uninitialized_var(__data); \ + int ret = bfq_var_store(&__data, (page), count); \ + if (__data < (MIN)) \ + __data = (MIN); \ + else if (__data > (MAX)) \ + __data = (MAX); \ + if (__CONV) \ + *(__PTR) = msecs_to_jiffies(__data); \ + else \ + *(__PTR) = __data; \ + return ret; \ +} +STORE_FUNCTION(bfq_quantum_store, &bfqd->bfq_quantum, 1, INT_MAX, 0); +STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1, + INT_MAX, 1); +STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1, + INT_MAX, 1); +STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0); +STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1, + INT_MAX, 0); +STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 1); +STORE_FUNCTION(bfq_max_budget_async_rq_store, &bfqd->bfq_max_budget_async_rq, + 1, INT_MAX, 0); +STORE_FUNCTION(bfq_timeout_async_store, &bfqd->bfq_timeout[BLK_RW_ASYNC], 0, + INT_MAX, 1); +STORE_FUNCTION(bfq_wr_coeff_store, &bfqd->bfq_wr_coeff, 1, INT_MAX, 0); +STORE_FUNCTION(bfq_wr_max_time_store, &bfqd->bfq_wr_max_time, 0, INT_MAX, 1); +STORE_FUNCTION(bfq_wr_rt_max_time_store, &bfqd->bfq_wr_rt_max_time, 0, INT_MAX, + 1); +STORE_FUNCTION(bfq_wr_min_idle_time_store, &bfqd->bfq_wr_min_idle_time, 0, + INT_MAX, 1); +STORE_FUNCTION(bfq_wr_min_inter_arr_async_store, + &bfqd->bfq_wr_min_inter_arr_async, 0, INT_MAX, 1); +STORE_FUNCTION(bfq_wr_max_softrt_rate_store, &bfqd->bfq_wr_max_softrt_rate, 0, + INT_MAX, 0); +#undef STORE_FUNCTION + +/* do nothing for the moment */ +static ssize_t bfq_weights_store(struct elevator_queue *e, + const char *page, size_t count) +{ + return count; +} + +static inline unsigned long bfq_estimated_max_budget(struct bfq_data *bfqd) +{ + u64 timeout = jiffies_to_msecs(bfqd->bfq_timeout[BLK_RW_SYNC]); + + if (bfqd->peak_rate_samples >= BFQ_PEAK_RATE_SAMPLES) + return bfq_calc_max_budget(bfqd->peak_rate, timeout); + else + return bfq_default_max_budget; +} + +static ssize_t bfq_max_budget_store(struct elevator_queue *e, + const char *page, size_t count) +{ + struct bfq_data *bfqd = e->elevator_data; + unsigned long uninitialized_var(__data); + int ret = bfq_var_store(&__data, (page), count); + + if (__data == 0) + bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd); + else { + if (__data > INT_MAX) + __data = INT_MAX; + bfqd->bfq_max_budget = __data; + } + + bfqd->bfq_user_max_budget = __data; + + return ret; +} + +static ssize_t bfq_timeout_sync_store(struct elevator_queue *e, + const char *page, size_t count) +{ + struct bfq_data *bfqd = e->elevator_data; + unsigned long uninitialized_var(__data); + int ret = bfq_var_store(&__data, (page), count); + + if (__data < 1) + __data = 1; + else if (__data > INT_MAX) + __data = INT_MAX; + + bfqd->bfq_timeout[BLK_RW_SYNC] = msecs_to_jiffies(__data); + if (bfqd->bfq_user_max_budget == 0) + bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd); + + return ret; +} + +static ssize_t bfq_low_latency_store(struct elevator_queue *e, + const char *page, size_t count) +{ + struct bfq_data *bfqd = e->elevator_data; + unsigned long uninitialized_var(__data); + int ret = bfq_var_store(&__data, (page), count); + + if (__data > 1) + __data = 1; + if (__data == 0 && bfqd->low_latency != 0) + bfq_end_wr(bfqd); + bfqd->low_latency = __data; + + return ret; +} + +#define BFQ_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, bfq_##name##_show, bfq_##name##_store) + +static struct elv_fs_entry bfq_attrs[] = { + BFQ_ATTR(quantum), + BFQ_ATTR(fifo_expire_sync), + BFQ_ATTR(fifo_expire_async), + BFQ_ATTR(back_seek_max), + BFQ_ATTR(back_seek_penalty), + BFQ_ATTR(slice_idle), + BFQ_ATTR(max_budget), + BFQ_ATTR(max_budget_async_rq), + BFQ_ATTR(timeout_sync), + BFQ_ATTR(timeout_async), + BFQ_ATTR(low_latency), + BFQ_ATTR(wr_coeff), + BFQ_ATTR(wr_max_time), + BFQ_ATTR(wr_rt_max_time), + BFQ_ATTR(wr_min_idle_time), + BFQ_ATTR(wr_min_inter_arr_async), + BFQ_ATTR(wr_max_softrt_rate), + BFQ_ATTR(weights), + __ATTR_NULL +}; + +static struct elevator_type iosched_bfq = { + .ops = { + .elevator_merge_fn = bfq_merge, + .elevator_merged_fn = bfq_merged_request, + .elevator_merge_req_fn = bfq_merged_requests, + .elevator_allow_merge_fn = bfq_allow_merge, + .elevator_dispatch_fn = bfq_dispatch_requests, + .elevator_add_req_fn = bfq_insert_request, + .elevator_activate_req_fn = bfq_activate_request, + .elevator_deactivate_req_fn = bfq_deactivate_request, + .elevator_completed_req_fn = bfq_completed_request, + .elevator_former_req_fn = elv_rb_former_request, + .elevator_latter_req_fn = elv_rb_latter_request, + .elevator_init_icq_fn = bfq_init_icq, + .elevator_exit_icq_fn = bfq_exit_icq, + .elevator_set_req_fn = bfq_set_request, + .elevator_put_req_fn = bfq_put_request, + .elevator_may_queue_fn = bfq_may_queue, + .elevator_init_fn = bfq_init_queue, + .elevator_exit_fn = bfq_exit_queue, + }, + .icq_size = sizeof(struct bfq_io_cq), + .icq_align = __alignof__(struct bfq_io_cq), + .elevator_attrs = bfq_attrs, + .elevator_name = "bfq", + .elevator_owner = THIS_MODULE, +}; + +static int __init bfq_init(void) +{ + /* + * Can be 0 on HZ < 1000 setups. + */ + if (bfq_slice_idle == 0) + bfq_slice_idle = 1; + + if (bfq_timeout_async == 0) + bfq_timeout_async = 1; + + if (bfq_slab_setup()) + return -ENOMEM; + + /* + * Times to load large popular applications for the typical systems + * installed on the reference devices (see the comments before the + * definitions of the two arrays). + */ + T_slow[0] = msecs_to_jiffies(2600); + T_slow[1] = msecs_to_jiffies(1000); + T_fast[0] = msecs_to_jiffies(5500); + T_fast[1] = msecs_to_jiffies(2000); + + /* + * Thresholds that determine the switch between speed classes (see + * the comments before the definition of the array). + */ + device_speed_thresh[0] = (R_fast[0] + R_slow[0]) / 2; + device_speed_thresh[1] = (R_fast[1] + R_slow[1]) / 2; + + elv_register(&iosched_bfq); + pr_info("BFQ I/O-scheduler version: v7r7"); + + return 0; +} + +static void __exit bfq_exit(void) +{ + elv_unregister(&iosched_bfq); + bfq_slab_kill(); +} + +module_init(bfq_init); +module_exit(bfq_exit); + +MODULE_AUTHOR("Fabio Checconi, Paolo Valente"); +MODULE_LICENSE("GPL"); diff --git a/block/bfq-sched.c b/block/bfq-sched.c new file mode 100644 index 0000000..6764a7e --- /dev/null +++ b/block/bfq-sched.c @@ -0,0 +1,1186 @@ +/* + * BFQ: Hierarchical B-WF2Q+ scheduler. + * + * Based on ideas and code from CFQ: + * Copyright (C) 2003 Jens Axboe + * + * Copyright (C) 2008 Fabio Checconi + * Paolo Valente + * + * Copyright (C) 2010 Paolo Valente + */ + +#ifdef CONFIG_CGROUP_BFQIO +#define for_each_entity(entity) \ + for (; entity != NULL; entity = entity->parent) + +#define for_each_entity_safe(entity, parent) \ + for (; entity && ({ parent = entity->parent; 1; }); entity = parent) + +static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, + int extract, + struct bfq_data *bfqd); + +static inline void bfq_update_budget(struct bfq_entity *next_in_service) +{ + struct bfq_entity *bfqg_entity; + struct bfq_group *bfqg; + struct bfq_sched_data *group_sd; + + BUG_ON(next_in_service == NULL); + + group_sd = next_in_service->sched_data; + + bfqg = container_of(group_sd, struct bfq_group, sched_data); + /* + * bfq_group's my_entity field is not NULL only if the group + * is not the root group. We must not touch the root entity + * as it must never become an in-service entity. + */ + bfqg_entity = bfqg->my_entity; + if (bfqg_entity != NULL) + bfqg_entity->budget = next_in_service->budget; +} + +static int bfq_update_next_in_service(struct bfq_sched_data *sd) +{ + struct bfq_entity *next_in_service; + + if (sd->in_service_entity != NULL) + /* will update/requeue at the end of service */ + return 0; + + /* + * NOTE: this can be improved in many ways, such as returning + * 1 (and thus propagating upwards the update) only when the + * budget changes, or caching the bfqq that will be scheduled + * next from this subtree. By now we worry more about + * correctness than about performance... + */ + next_in_service = bfq_lookup_next_entity(sd, 0, NULL); + sd->next_in_service = next_in_service; + + if (next_in_service != NULL) + bfq_update_budget(next_in_service); + + return 1; +} + +static inline void bfq_check_next_in_service(struct bfq_sched_data *sd, + struct bfq_entity *entity) +{ + BUG_ON(sd->next_in_service != entity); +} +#else +#define for_each_entity(entity) \ + for (; entity != NULL; entity = NULL) + +#define for_each_entity_safe(entity, parent) \ + for (parent = NULL; entity != NULL; entity = parent) + +static inline int bfq_update_next_in_service(struct bfq_sched_data *sd) +{ + return 0; +} + +static inline void bfq_check_next_in_service(struct bfq_sched_data *sd, + struct bfq_entity *entity) +{ +} + +static inline void bfq_update_budget(struct bfq_entity *next_in_service) +{ +} +#endif + +/* + * Shift for timestamp calculations. This actually limits the maximum + * service allowed in one timestamp delta (small shift values increase it), + * the maximum total weight that can be used for the queues in the system + * (big shift values increase it), and the period of virtual time + * wraparounds. + */ +#define WFQ_SERVICE_SHIFT 22 + +/** + * bfq_gt - compare two timestamps. + * @a: first ts. + * @b: second ts. + * + * Return @a > @b, dealing with wrapping correctly. + */ +static inline int bfq_gt(u64 a, u64 b) +{ + return (s64)(a - b) > 0; +} + +static inline struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = NULL; + + BUG_ON(entity == NULL); + + if (entity->my_sched_data == NULL) + bfqq = container_of(entity, struct bfq_queue, entity); + + return bfqq; +} + + +/** + * bfq_delta - map service into the virtual time domain. + * @service: amount of service. + * @weight: scale factor (weight of an entity or weight sum). + */ +static inline u64 bfq_delta(unsigned long service, + unsigned long weight) +{ + u64 d = (u64)service << WFQ_SERVICE_SHIFT; + + do_div(d, weight); + return d; +} + +/** + * bfq_calc_finish - assign the finish time to an entity. + * @entity: the entity to act upon. + * @service: the service to be charged to the entity. + */ +static inline void bfq_calc_finish(struct bfq_entity *entity, + unsigned long service) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + + BUG_ON(entity->weight == 0); + + entity->finish = entity->start + + bfq_delta(service, entity->weight); + + if (bfqq != NULL) { + bfq_log_bfqq(bfqq->bfqd, bfqq, + "calc_finish: serv %lu, w %d", + service, entity->weight); + bfq_log_bfqq(bfqq->bfqd, bfqq, + "calc_finish: start %llu, finish %llu, delta %llu", + entity->start, entity->finish, + bfq_delta(service, entity->weight)); + } +} + +/** + * bfq_entity_of - get an entity from a node. + * @node: the node field of the entity. + * + * Convert a node pointer to the relative entity. This is used only + * to simplify the logic of some functions and not as the generic + * conversion mechanism because, e.g., in the tree walking functions, + * the check for a %NULL value would be redundant. + */ +static inline struct bfq_entity *bfq_entity_of(struct rb_node *node) +{ + struct bfq_entity *entity = NULL; + + if (node != NULL) + entity = rb_entry(node, struct bfq_entity, rb_node); + + return entity; +} + +/** + * bfq_extract - remove an entity from a tree. + * @root: the tree root. + * @entity: the entity to remove. + */ +static inline void bfq_extract(struct rb_root *root, + struct bfq_entity *entity) +{ + BUG_ON(entity->tree != root); + + entity->tree = NULL; + rb_erase(&entity->rb_node, root); +} + +/** + * bfq_idle_extract - extract an entity from the idle tree. + * @st: the service tree of the owning @entity. + * @entity: the entity being removed. + */ +static void bfq_idle_extract(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct rb_node *next; + + BUG_ON(entity->tree != &st->idle); + + if (entity == st->first_idle) { + next = rb_next(&entity->rb_node); + st->first_idle = bfq_entity_of(next); + } + + if (entity == st->last_idle) { + next = rb_prev(&entity->rb_node); + st->last_idle = bfq_entity_of(next); + } + + bfq_extract(&st->idle, entity); + + if (bfqq != NULL) + list_del(&bfqq->bfqq_list); +} + +/** + * bfq_insert - generic tree insertion. + * @root: tree root. + * @entity: entity to insert. + * + * This is used for the idle and the active tree, since they are both + * ordered by finish time. + */ +static void bfq_insert(struct rb_root *root, struct bfq_entity *entity) +{ + struct bfq_entity *entry; + struct rb_node **node = &root->rb_node; + struct rb_node *parent = NULL; + + BUG_ON(entity->tree != NULL); + + while (*node != NULL) { + parent = *node; + entry = rb_entry(parent, struct bfq_entity, rb_node); + + if (bfq_gt(entry->finish, entity->finish)) + node = &parent->rb_left; + else + node = &parent->rb_right; + } + + rb_link_node(&entity->rb_node, parent, node); + rb_insert_color(&entity->rb_node, root); + + entity->tree = root; +} + +/** + * bfq_update_min - update the min_start field of a entity. + * @entity: the entity to update. + * @node: one of its children. + * + * This function is called when @entity may store an invalid value for + * min_start due to updates to the active tree. The function assumes + * that the subtree rooted at @node (which may be its left or its right + * child) has a valid min_start value. + */ +static inline void bfq_update_min(struct bfq_entity *entity, + struct rb_node *node) +{ + struct bfq_entity *child; + + if (node != NULL) { + child = rb_entry(node, struct bfq_entity, rb_node); + if (bfq_gt(entity->min_start, child->min_start)) + entity->min_start = child->min_start; + } +} + +/** + * bfq_update_active_node - recalculate min_start. + * @node: the node to update. + * + * @node may have changed position or one of its children may have moved, + * this function updates its min_start value. The left and right subtrees + * are assumed to hold a correct min_start value. + */ +static inline void bfq_update_active_node(struct rb_node *node) +{ + struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node); + + entity->min_start = entity->start; + bfq_update_min(entity, node->rb_right); + bfq_update_min(entity, node->rb_left); +} + +/** + * bfq_update_active_tree - update min_start for the whole active tree. + * @node: the starting node. + * + * @node must be the deepest modified node after an update. This function + * updates its min_start using the values held by its children, assuming + * that they did not change, and then updates all the nodes that may have + * changed in the path to the root. The only nodes that may have changed + * are the ones in the path or their siblings. + */ +static void bfq_update_active_tree(struct rb_node *node) +{ + struct rb_node *parent; + +up: + bfq_update_active_node(node); + + parent = rb_parent(node); + if (parent == NULL) + return; + + if (node == parent->rb_left && parent->rb_right != NULL) + bfq_update_active_node(parent->rb_right); + else if (parent->rb_left != NULL) + bfq_update_active_node(parent->rb_left); + + node = parent; + goto up; +} + +static void bfq_weights_tree_add(struct bfq_data *bfqd, + struct bfq_entity *entity, + struct rb_root *root); + +static void bfq_weights_tree_remove(struct bfq_data *bfqd, + struct bfq_entity *entity, + struct rb_root *root); + + +/** + * bfq_active_insert - insert an entity in the active tree of its + * group/device. + * @st: the service tree of the entity. + * @entity: the entity being inserted. + * + * The active tree is ordered by finish time, but an extra key is kept + * per each node, containing the minimum value for the start times of + * its children (and the node itself), so it's possible to search for + * the eligible node with the lowest finish time in logarithmic time. + */ +static void bfq_active_insert(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct rb_node *node = &entity->rb_node; +#ifdef CONFIG_CGROUP_BFQIO + struct bfq_sched_data *sd = NULL; + struct bfq_group *bfqg = NULL; + struct bfq_data *bfqd = NULL; +#endif + + bfq_insert(&st->active, entity); + + if (node->rb_left != NULL) + node = node->rb_left; + else if (node->rb_right != NULL) + node = node->rb_right; + + bfq_update_active_tree(node); + +#ifdef CONFIG_CGROUP_BFQIO + sd = entity->sched_data; + bfqg = container_of(sd, struct bfq_group, sched_data); + BUG_ON(!bfqg); + bfqd = (struct bfq_data *)bfqg->bfqd; +#endif + if (bfqq != NULL) + list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list); +#ifdef CONFIG_CGROUP_BFQIO + else { /* bfq_group */ + BUG_ON(!bfqd); + bfq_weights_tree_add(bfqd, entity, &bfqd->group_weights_tree); + } + if (bfqg != bfqd->root_group) { + BUG_ON(!bfqg); + BUG_ON(!bfqd); + bfqg->active_entities++; + if (bfqg->active_entities == 2) + bfqd->active_numerous_groups++; + } +#endif +} + +/** + * bfq_ioprio_to_weight - calc a weight from an ioprio. + * @ioprio: the ioprio value to convert. + */ +static inline unsigned short bfq_ioprio_to_weight(int ioprio) +{ + BUG_ON(ioprio < 0 || ioprio >= IOPRIO_BE_NR); + return IOPRIO_BE_NR - ioprio; +} + +/** + * bfq_weight_to_ioprio - calc an ioprio from a weight. + * @weight: the weight value to convert. + * + * To preserve as mush as possible the old only-ioprio user interface, + * 0 is used as an escape ioprio value for weights (numerically) equal or + * larger than IOPRIO_BE_NR + */ +static inline unsigned short bfq_weight_to_ioprio(int weight) +{ + BUG_ON(weight < BFQ_MIN_WEIGHT || weight > BFQ_MAX_WEIGHT); + return IOPRIO_BE_NR - weight < 0 ? 0 : IOPRIO_BE_NR - weight; +} + +static inline void bfq_get_entity(struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + + if (bfqq != NULL) { + atomic_inc(&bfqq->ref); + bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d", + bfqq, atomic_read(&bfqq->ref)); + } +} + +/** + * bfq_find_deepest - find the deepest node that an extraction can modify. + * @node: the node being removed. + * + * Do the first step of an extraction in an rb tree, looking for the + * node that will replace @node, and returning the deepest node that + * the following modifications to the tree can touch. If @node is the + * last node in the tree return %NULL. + */ +static struct rb_node *bfq_find_deepest(struct rb_node *node) +{ + struct rb_node *deepest; + + if (node->rb_right == NULL && node->rb_left == NULL) + deepest = rb_parent(node); + else if (node->rb_right == NULL) + deepest = node->rb_left; + else if (node->rb_left == NULL) + deepest = node->rb_right; + else { + deepest = rb_next(node); + if (deepest->rb_right != NULL) + deepest = deepest->rb_right; + else if (rb_parent(deepest) != node) + deepest = rb_parent(deepest); + } + + return deepest; +} + +/** + * bfq_active_extract - remove an entity from the active tree. + * @st: the service_tree containing the tree. + * @entity: the entity being removed. + */ +static void bfq_active_extract(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct rb_node *node; +#ifdef CONFIG_CGROUP_BFQIO + struct bfq_sched_data *sd = NULL; + struct bfq_group *bfqg = NULL; + struct bfq_data *bfqd = NULL; +#endif + + node = bfq_find_deepest(&entity->rb_node); + bfq_extract(&st->active, entity); + + if (node != NULL) + bfq_update_active_tree(node); + +#ifdef CONFIG_CGROUP_BFQIO + sd = entity->sched_data; + bfqg = container_of(sd, struct bfq_group, sched_data); + BUG_ON(!bfqg); + bfqd = (struct bfq_data *)bfqg->bfqd; +#endif + if (bfqq != NULL) + list_del(&bfqq->bfqq_list); +#ifdef CONFIG_CGROUP_BFQIO + else { /* bfq_group */ + BUG_ON(!bfqd); + bfq_weights_tree_remove(bfqd, entity, + &bfqd->group_weights_tree); + } + if (bfqg != bfqd->root_group) { + BUG_ON(!bfqg); + BUG_ON(!bfqd); + BUG_ON(!bfqg->active_entities); + bfqg->active_entities--; + if (bfqg->active_entities == 1) { + BUG_ON(!bfqd->active_numerous_groups); + bfqd->active_numerous_groups--; + } + } +#endif +} + +/** + * bfq_idle_insert - insert an entity into the idle tree. + * @st: the service tree containing the tree. + * @entity: the entity to insert. + */ +static void bfq_idle_insert(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct bfq_entity *first_idle = st->first_idle; + struct bfq_entity *last_idle = st->last_idle; + + if (first_idle == NULL || bfq_gt(first_idle->finish, entity->finish)) + st->first_idle = entity; + if (last_idle == NULL || bfq_gt(entity->finish, last_idle->finish)) + st->last_idle = entity; + + bfq_insert(&st->idle, entity); + + if (bfqq != NULL) + list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list); +} + +/** + * bfq_forget_entity - remove an entity from the wfq trees. + * @st: the service tree. + * @entity: the entity being removed. + * + * Update the device status and forget everything about @entity, putting + * the device reference to it, if it is a queue. Entities belonging to + * groups are not refcounted. + */ +static void bfq_forget_entity(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + struct bfq_sched_data *sd; + + BUG_ON(!entity->on_st); + + entity->on_st = 0; + st->wsum -= entity->weight; + if (bfqq != NULL) { + sd = entity->sched_data; + bfq_log_bfqq(bfqq->bfqd, bfqq, "forget_entity: %p %d", + bfqq, atomic_read(&bfqq->ref)); + bfq_put_queue(bfqq); + } +} + +/** + * bfq_put_idle_entity - release the idle tree ref of an entity. + * @st: service tree for the entity. + * @entity: the entity being released. + */ +static void bfq_put_idle_entity(struct bfq_service_tree *st, + struct bfq_entity *entity) +{ + bfq_idle_extract(st, entity); + bfq_forget_entity(st, entity); +} + +/** + * bfq_forget_idle - update the idle tree if necessary. + * @st: the service tree to act upon. + * + * To preserve the global O(log N) complexity we only remove one entry here; + * as the idle tree will not grow indefinitely this can be done safely. + */ +static void bfq_forget_idle(struct bfq_service_tree *st) +{ + struct bfq_entity *first_idle = st->first_idle; + struct bfq_entity *last_idle = st->last_idle; + + if (RB_EMPTY_ROOT(&st->active) && last_idle != NULL && + !bfq_gt(last_idle->finish, st->vtime)) { + /* + * Forget the whole idle tree, increasing the vtime past + * the last finish time of idle entities. + */ + st->vtime = last_idle->finish; + } + + if (first_idle != NULL && !bfq_gt(first_idle->finish, st->vtime)) + bfq_put_idle_entity(st, first_idle); +} + +static struct bfq_service_tree * +__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st, + struct bfq_entity *entity) +{ + struct bfq_service_tree *new_st = old_st; + + if (entity->ioprio_changed) { + struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); + unsigned short prev_weight, new_weight; + struct bfq_data *bfqd = NULL; + struct rb_root *root; +#ifdef CONFIG_CGROUP_BFQIO + struct bfq_sched_data *sd; + struct bfq_group *bfqg; +#endif + + if (bfqq != NULL) + bfqd = bfqq->bfqd; +#ifdef CONFIG_CGROUP_BFQIO + else { + sd = entity->my_sched_data; + bfqg = container_of(sd, struct bfq_group, sched_data); + BUG_ON(!bfqg); + bfqd = (struct bfq_data *)bfqg->bfqd; + BUG_ON(!bfqd); + } +#endif + + BUG_ON(old_st->wsum < entity->weight); + old_st->wsum -= entity->weight; + + if (entity->new_weight != entity->orig_weight) { + if (entity->new_weight < BFQ_MIN_WEIGHT || + entity->new_weight > BFQ_MAX_WEIGHT) { + printk(KERN_CRIT "update_weight_prio: " + "new_weight %d\n", + entity->new_weight); + BUG(); + } + entity->orig_weight = entity->new_weight; + entity->ioprio = + bfq_weight_to_ioprio(entity->orig_weight); + } else if (entity->new_ioprio != entity->ioprio) { + entity->ioprio = entity->new_ioprio; + entity->orig_weight = + bfq_ioprio_to_weight(entity->ioprio); + } else + entity->new_weight = entity->orig_weight = + bfq_ioprio_to_weight(entity->ioprio); + + entity->ioprio_class = entity->new_ioprio_class; + entity->ioprio_changed = 0; + + /* + * NOTE: here we may be changing the weight too early, + * this will cause unfairness. The correct approach + * would have required additional complexity to defer + * weight changes to the proper time instants (i.e., + * when entity->finish <= old_st->vtime). + */ + new_st = bfq_entity_service_tree(entity); + + prev_weight = entity->weight; + new_weight = entity->orig_weight * + (bfqq != NULL ? bfqq->wr_coeff : 1); + /* + * If the weight of the entity changes, remove the entity + * from its old weight counter (if there is a counter + * associated with the entity), and add it to the counter + * associated with its new weight. + */ + if (prev_weight != new_weight) { + root = bfqq ? &bfqd->queue_weights_tree : + &bfqd->group_weights_tree; + bfq_weights_tree_remove(bfqd, entity, root); + } + entity->weight = new_weight; + /* + * Add the entity to its weights tree only if it is + * not associated with a weight-raised queue. + */ + if (prev_weight != new_weight && + (bfqq ? bfqq->wr_coeff == 1 : 1)) + /* If we get here, root has been initialized. */ + bfq_weights_tree_add(bfqd, entity, root); + + new_st->wsum += entity->weight; + + if (new_st != old_st) + entity->start = new_st->vtime; + } + + return new_st; +} + +/** + * bfq_bfqq_served - update the scheduler status after selection for + * service. + * @bfqq: the queue being served. + * @served: bytes to transfer. + * + * NOTE: this can be optimized, as the timestamps of upper level entities + * are synchronized every time a new bfqq is selected for service. By now, + * we keep it to better check consistency. + */ +static void bfq_bfqq_served(struct bfq_queue *bfqq, unsigned long served) +{ + struct bfq_entity *entity = &bfqq->entity; + struct bfq_service_tree *st; + + for_each_entity(entity) { + st = bfq_entity_service_tree(entity); + + entity->service += served; + BUG_ON(entity->service > entity->budget); + BUG_ON(st->wsum == 0); + + st->vtime += bfq_delta(served, st->wsum); + bfq_forget_idle(st); + } + bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %lu secs", served); +} + +/** + * bfq_bfqq_charge_full_budget - set the service to the entity budget. + * @bfqq: the queue that needs a service update. + * + * When it's not possible to be fair in the service domain, because + * a queue is not consuming its budget fast enough (the meaning of + * fast depends on the timeout parameter), we charge it a full + * budget. In this way we should obtain a sort of time-domain + * fairness among all the seeky/slow queues. + */ +static inline void bfq_bfqq_charge_full_budget(struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + + bfq_log_bfqq(bfqq->bfqd, bfqq, "charge_full_budget"); + + bfq_bfqq_served(bfqq, entity->budget - entity->service); +} + +/** + * __bfq_activate_entity - activate an entity. + * @entity: the entity being activated. + * + * Called whenever an entity is activated, i.e., it is not active and one + * of its children receives a new request, or has to be reactivated due to + * budget exhaustion. It uses the current budget of the entity (and the + * service received if @entity is active) of the queue to calculate its + * timestamps. + */ +static void __bfq_activate_entity(struct bfq_entity *entity) +{ + struct bfq_sched_data *sd = entity->sched_data; + struct bfq_service_tree *st = bfq_entity_service_tree(entity); + + if (entity == sd->in_service_entity) { + BUG_ON(entity->tree != NULL); + /* + * If we are requeueing the current entity we have + * to take care of not charging to it service it has + * not received. + */ + bfq_calc_finish(entity, entity->service); + entity->start = entity->finish; + sd->in_service_entity = NULL; + } else if (entity->tree == &st->active) { + /* + * Requeueing an entity due to a change of some + * next_in_service entity below it. We reuse the + * old start time. + */ + bfq_active_extract(st, entity); + } else if (entity->tree == &st->idle) { + /* + * Must be on the idle tree, bfq_idle_extract() will + * check for that. + */ + bfq_idle_extract(st, entity); + entity->start = bfq_gt(st->vtime, entity->finish) ? + st->vtime : entity->finish; + } else { + /* + * The finish time of the entity may be invalid, and + * it is in the past for sure, otherwise the queue + * would have been on the idle tree. + */ + entity->start = st->vtime; + st->wsum += entity->weight; + bfq_get_entity(entity); + + BUG_ON(entity->on_st); + entity->on_st = 1; + } + + st = __bfq_entity_update_weight_prio(st, entity); + bfq_calc_finish(entity, entity->budget); + bfq_active_insert(st, entity); +} + +/** + * bfq_activate_entity - activate an entity and its ancestors if necessary. + * @entity: the entity to activate. + * + * Activate @entity and all the entities on the path from it to the root. + */ +static void bfq_activate_entity(struct bfq_entity *entity) +{ + struct bfq_sched_data *sd; + + for_each_entity(entity) { + __bfq_activate_entity(entity); + + sd = entity->sched_data; + if (!bfq_update_next_in_service(sd)) + /* + * No need to propagate the activation to the + * upper entities, as they will be updated when + * the in-service entity is rescheduled. + */ + break; + } +} + +/** + * __bfq_deactivate_entity - deactivate an entity from its service tree. + * @entity: the entity to deactivate. + * @requeue: if false, the entity will not be put into the idle tree. + * + * Deactivate an entity, independently from its previous state. If the + * entity was not on a service tree just return, otherwise if it is on + * any scheduler tree, extract it from that tree, and if necessary + * and if the caller did not specify @requeue, put it on the idle tree. + * + * Return %1 if the caller should update the entity hierarchy, i.e., + * if the entity was in service or if it was the next_in_service for + * its sched_data; return %0 otherwise. + */ +static int __bfq_deactivate_entity(struct bfq_entity *entity, int requeue) +{ + struct bfq_sched_data *sd = entity->sched_data; + struct bfq_service_tree *st = bfq_entity_service_tree(entity); + int was_in_service = entity == sd->in_service_entity; + int ret = 0; + + if (!entity->on_st) + return 0; + + BUG_ON(was_in_service && entity->tree != NULL); + + if (was_in_service) { + bfq_calc_finish(entity, entity->service); + sd->in_service_entity = NULL; + } else if (entity->tree == &st->active) + bfq_active_extract(st, entity); + else if (entity->tree == &st->idle) + bfq_idle_extract(st, entity); + else if (entity->tree != NULL) + BUG(); + + if (was_in_service || sd->next_in_service == entity) + ret = bfq_update_next_in_service(sd); + + if (!requeue || !bfq_gt(entity->finish, st->vtime)) + bfq_forget_entity(st, entity); + else + bfq_idle_insert(st, entity); + + BUG_ON(sd->in_service_entity == entity); + BUG_ON(sd->next_in_service == entity); + + return ret; +} + +/** + * bfq_deactivate_entity - deactivate an entity. + * @entity: the entity to deactivate. + * @requeue: true if the entity can be put on the idle tree + */ +static void bfq_deactivate_entity(struct bfq_entity *entity, int requeue) +{ + struct bfq_sched_data *sd; + struct bfq_entity *parent; + + for_each_entity_safe(entity, parent) { + sd = entity->sched_data; + + if (!__bfq_deactivate_entity(entity, requeue)) + /* + * The parent entity is still backlogged, and + * we don't need to update it as it is still + * in service. + */ + break; + + if (sd->next_in_service != NULL) + /* + * The parent entity is still backlogged and + * the budgets on the path towards the root + * need to be updated. + */ + goto update; + + /* + * If we reach there the parent is no more backlogged and + * we want to propagate the dequeue upwards. + */ + requeue = 1; + } + + return; + +update: + entity = parent; + for_each_entity(entity) { + __bfq_activate_entity(entity); + + sd = entity->sched_data; + if (!bfq_update_next_in_service(sd)) + break; + } +} + +/** + * bfq_update_vtime - update vtime if necessary. + * @st: the service tree to act upon. + * + * If necessary update the service tree vtime to have at least one + * eligible entity, skipping to its start time. Assumes that the + * active tree of the device is not empty. + * + * NOTE: this hierarchical implementation updates vtimes quite often, + * we may end up with reactivated processes getting timestamps after a + * vtime skip done because we needed a ->first_active entity on some + * intermediate node. + */ +static void bfq_update_vtime(struct bfq_service_tree *st) +{ + struct bfq_entity *entry; + struct rb_node *node = st->active.rb_node; + + entry = rb_entry(node, struct bfq_entity, rb_node); + if (bfq_gt(entry->min_start, st->vtime)) { + st->vtime = entry->min_start; + bfq_forget_idle(st); + } +} + +/** + * bfq_first_active_entity - find the eligible entity with + * the smallest finish time + * @st: the service tree to select from. + * + * This function searches the first schedulable entity, starting from the + * root of the tree and going on the left every time on this side there is + * a subtree with at least one eligible (start >= vtime) entity. The path on + * the right is followed only if a) the left subtree contains no eligible + * entities and b) no eligible entity has been found yet. + */ +static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st) +{ + struct bfq_entity *entry, *first = NULL; + struct rb_node *node = st->active.rb_node; + + while (node != NULL) { + entry = rb_entry(node, struct bfq_entity, rb_node); +left: + if (!bfq_gt(entry->start, st->vtime)) + first = entry; + + BUG_ON(bfq_gt(entry->min_start, st->vtime)); + + if (node->rb_left != NULL) { + entry = rb_entry(node->rb_left, + struct bfq_entity, rb_node); + if (!bfq_gt(entry->min_start, st->vtime)) { + node = node->rb_left; + goto left; + } + } + if (first != NULL) + break; + node = node->rb_right; + } + + BUG_ON(first == NULL && !RB_EMPTY_ROOT(&st->active)); + return first; +} + +/** + * __bfq_lookup_next_entity - return the first eligible entity in @st. + * @st: the service tree. + * + * Update the virtual time in @st and return the first eligible entity + * it contains. + */ +static struct bfq_entity *__bfq_lookup_next_entity(struct bfq_service_tree *st, + bool force) +{ + struct bfq_entity *entity, *new_next_in_service = NULL; + + if (RB_EMPTY_ROOT(&st->active)) + return NULL; + + bfq_update_vtime(st); + entity = bfq_first_active_entity(st); + BUG_ON(bfq_gt(entity->start, st->vtime)); + + /* + * If the chosen entity does not match with the sched_data's + * next_in_service and we are forcedly serving the IDLE priority + * class tree, bubble up budget update. + */ + if (unlikely(force && entity != entity->sched_data->next_in_service)) { + new_next_in_service = entity; + for_each_entity(new_next_in_service) + bfq_update_budget(new_next_in_service); + } + + return entity; +} + +/** + * bfq_lookup_next_entity - return the first eligible entity in @sd. + * @sd: the sched_data. + * @extract: if true the returned entity will be also extracted from @sd. + * + * NOTE: since we cache the next_in_service entity at each level of the + * hierarchy, the complexity of the lookup can be decreased with + * absolutely no effort just returning the cached next_in_service value; + * we prefer to do full lookups to test the consistency of * the data + * structures. + */ +static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, + int extract, + struct bfq_data *bfqd) +{ + struct bfq_service_tree *st = sd->service_tree; + struct bfq_entity *entity; + int i = 0; + + BUG_ON(sd->in_service_entity != NULL); + + if (bfqd != NULL && + jiffies - bfqd->bfq_class_idle_last_service > BFQ_CL_IDLE_TIMEOUT) { + entity = __bfq_lookup_next_entity(st + BFQ_IOPRIO_CLASSES - 1, + true); + if (entity != NULL) { + i = BFQ_IOPRIO_CLASSES - 1; + bfqd->bfq_class_idle_last_service = jiffies; + sd->next_in_service = entity; + } + } + for (; i < BFQ_IOPRIO_CLASSES; i++) { + entity = __bfq_lookup_next_entity(st + i, false); + if (entity != NULL) { + if (extract) { + bfq_check_next_in_service(sd, entity); + bfq_active_extract(st + i, entity); + sd->in_service_entity = entity; + sd->next_in_service = NULL; + } + break; + } + } + + return entity; +} + +/* + * Get next queue for service. + */ +static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd) +{ + struct bfq_entity *entity = NULL; + struct bfq_sched_data *sd; + struct bfq_queue *bfqq; + + BUG_ON(bfqd->in_service_queue != NULL); + + if (bfqd->busy_queues == 0) + return NULL; + + sd = &bfqd->root_group->sched_data; + for (; sd != NULL; sd = entity->my_sched_data) { + entity = bfq_lookup_next_entity(sd, 1, bfqd); + BUG_ON(entity == NULL); + entity->service = 0; + } + + bfqq = bfq_entity_to_bfqq(entity); + BUG_ON(bfqq == NULL); + + return bfqq; +} + +static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) +{ + if (bfqd->in_service_bic != NULL) { + put_io_context(bfqd->in_service_bic->icq.ioc); + bfqd->in_service_bic = NULL; + } + + bfqd->in_service_queue = NULL; + del_timer(&bfqd->idle_slice_timer); +} + +static void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, + int requeue) +{ + struct bfq_entity *entity = &bfqq->entity; + + if (bfqq == bfqd->in_service_queue) + __bfq_bfqd_reset_in_service(bfqd); + + bfq_deactivate_entity(entity, requeue); +} + +static void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + struct bfq_entity *entity = &bfqq->entity; + + bfq_activate_entity(entity); +} + +/* + * Called when the bfqq no longer has requests pending, remove it from + * the service tree. + */ +static void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq, + int requeue) +{ + BUG_ON(!bfq_bfqq_busy(bfqq)); + BUG_ON(!RB_EMPTY_ROOT(&bfqq->sort_list)); + + bfq_log_bfqq(bfqd, bfqq, "del from busy"); + + bfq_clear_bfqq_busy(bfqq); + + BUG_ON(bfqd->busy_queues == 0); + bfqd->busy_queues--; + + if (!bfqq->dispatched) { + bfq_weights_tree_remove(bfqd, &bfqq->entity, + &bfqd->queue_weights_tree); + if (!blk_queue_nonrot(bfqd->queue)) { + BUG_ON(!bfqd->busy_in_flight_queues); + bfqd->busy_in_flight_queues--; + if (bfq_bfqq_constantly_seeky(bfqq)) { + BUG_ON(!bfqd-> + const_seeky_busy_in_flight_queues); + bfqd->const_seeky_busy_in_flight_queues--; + } + } + } + if (bfqq->wr_coeff > 1) + bfqd->wr_busy_queues--; + + bfq_deactivate_bfqq(bfqd, bfqq, requeue); +} + +/* + * Called when an inactive queue receives a new request. + */ +static void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq) +{ + BUG_ON(bfq_bfqq_busy(bfqq)); + BUG_ON(bfqq == bfqd->in_service_queue); + + bfq_log_bfqq(bfqd, bfqq, "add to busy"); + + bfq_activate_bfqq(bfqd, bfqq); + + bfq_mark_bfqq_busy(bfqq); + bfqd->busy_queues++; + + if (!bfqq->dispatched) { + if (bfqq->wr_coeff == 1) + bfq_weights_tree_add(bfqd, &bfqq->entity, + &bfqd->queue_weights_tree); + if (!blk_queue_nonrot(bfqd->queue)) { + bfqd->busy_in_flight_queues++; + if (bfq_bfqq_constantly_seeky(bfqq)) + bfqd->const_seeky_busy_in_flight_queues++; + } + } + if (bfqq->wr_coeff > 1) + bfqd->wr_busy_queues++; +} diff --git a/block/bfq.h b/block/bfq.h new file mode 100644 index 0000000..9428d71 --- /dev/null +++ b/block/bfq.h @@ -0,0 +1,809 @@ +/* + * BFQ-v7r7 for 3.4.0: data structures and common functions prototypes. + * + * Based on ideas and code from CFQ: + * Copyright (C) 2003 Jens Axboe + * + * Copyright (C) 2008 Fabio Checconi + * Paolo Valente + * + * Copyright (C) 2010 Paolo Valente + */ + +#ifndef _BFQ_H +#define _BFQ_H + +#include +#include +#include +#include + +#define BFQ_IOPRIO_CLASSES 3 +#define BFQ_CL_IDLE_TIMEOUT (HZ/5) + +#define BFQ_MIN_WEIGHT 1 +#define BFQ_MAX_WEIGHT 1000 + +#define BFQ_DEFAULT_QUEUE_IOPRIO 4 + +#define BFQ_DEFAULT_GRP_WEIGHT 10 +#define BFQ_DEFAULT_GRP_IOPRIO 0 +#define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE + +struct bfq_entity; + +/** + * struct bfq_service_tree - per ioprio_class service tree. + * @active: tree for active entities (i.e., those backlogged). + * @idle: tree for idle entities (i.e., those not backlogged, with V <= F_i). + * @first_idle: idle entity with minimum F_i. + * @last_idle: idle entity with maximum F_i. + * @vtime: scheduler virtual time. + * @wsum: scheduler weight sum; active and idle entities contribute to it. + * + * Each service tree represents a B-WF2Q+ scheduler on its own. Each + * ioprio_class has its own independent scheduler, and so its own + * bfq_service_tree. All the fields are protected by the queue lock + * of the containing bfqd. + */ +struct bfq_service_tree { + struct rb_root active; + struct rb_root idle; + + struct bfq_entity *first_idle; + struct bfq_entity *last_idle; + + u64 vtime; + unsigned long wsum; +}; + +/** + * struct bfq_sched_data - multi-class scheduler. + * @in_service_entity: entity in service. + * @next_in_service: head-of-the-line entity in the scheduler. + * @service_tree: array of service trees, one per ioprio_class. + * + * bfq_sched_data is the basic scheduler queue. It supports three + * ioprio_classes, and can be used either as a toplevel queue or as + * an intermediate queue on a hierarchical setup. + * @next_in_service points to the active entity of the sched_data + * service trees that will be scheduled next. + * + * The supported ioprio_classes are the same as in CFQ, in descending + * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE. + * Requests from higher priority queues are served before all the + * requests from lower priority queues; among requests of the same + * queue requests are served according to B-WF2Q+. + * All the fields are protected by the queue lock of the containing bfqd. + */ +struct bfq_sched_data { + struct bfq_entity *in_service_entity; + struct bfq_entity *next_in_service; + struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES]; +}; + +/** + * struct bfq_weight_counter - counter of the number of all active entities + * with a given weight. + * @weight: weight of the entities that this counter refers to. + * @num_active: number of active entities with this weight. + * @weights_node: weights tree member (see bfq_data's @queue_weights_tree + * and @group_weights_tree). + */ +struct bfq_weight_counter { + short int weight; + unsigned int num_active; + struct rb_node weights_node; +}; + +/** + * struct bfq_entity - schedulable entity. + * @rb_node: service_tree member. + * @weight_counter: pointer to the weight counter associated with this entity. + * @on_st: flag, true if the entity is on a tree (either the active or + * the idle one of its service_tree). + * @finish: B-WF2Q+ finish timestamp (aka F_i). + * @start: B-WF2Q+ start timestamp (aka S_i). + * @tree: tree the entity is enqueued into; %NULL if not on a tree. + * @min_start: minimum start time of the (active) subtree rooted at + * this entity; used for O(log N) lookups into active trees. + * @service: service received during the last round of service. + * @budget: budget used to calculate F_i; F_i = S_i + @budget / @weight. + * @weight: weight of the queue + * @parent: parent entity, for hierarchical scheduling. + * @my_sched_data: for non-leaf nodes in the cgroup hierarchy, the + * associated scheduler queue, %NULL on leaf nodes. + * @sched_data: the scheduler queue this entity belongs to. + * @ioprio: the ioprio in use. + * @new_weight: when a weight change is requested, the new weight value. + * @orig_weight: original weight, used to implement weight boosting + * @new_ioprio: when an ioprio change is requested, the new ioprio value. + * @ioprio_class: the ioprio_class in use. + * @new_ioprio_class: when an ioprio_class change is requested, the new + * ioprio_class value. + * @ioprio_changed: flag, true when the user requested a weight, ioprio or + * ioprio_class change. + * + * A bfq_entity is used to represent either a bfq_queue (leaf node in the + * cgroup hierarchy) or a bfq_group into the upper level scheduler. Each + * entity belongs to the sched_data of the parent group in the cgroup + * hierarchy. Non-leaf entities have also their own sched_data, stored + * in @my_sched_data. + * + * Each entity stores independently its priority values; this would + * allow different weights on different devices, but this + * functionality is not exported to userspace by now. Priorities and + * weights are updated lazily, first storing the new values into the + * new_* fields, then setting the @ioprio_changed flag. As soon as + * there is a transition in the entity state that allows the priority + * update to take place the effective and the requested priority + * values are synchronized. + * + * Unless cgroups are used, the weight value is calculated from the + * ioprio to export the same interface as CFQ. When dealing with + * ``well-behaved'' queues (i.e., queues that do not spend too much + * time to consume their budget and have true sequential behavior, and + * when there are no external factors breaking anticipation) the + * relative weights at each level of the cgroups hierarchy should be + * guaranteed. All the fields are protected by the queue lock of the + * containing bfqd. + */ +struct bfq_entity { + struct rb_node rb_node; + struct bfq_weight_counter *weight_counter; + + int on_st; + + u64 finish; + u64 start; + + struct rb_root *tree; + + u64 min_start; + + unsigned long service, budget; + unsigned short weight, new_weight; + unsigned short orig_weight; + + struct bfq_entity *parent; + + struct bfq_sched_data *my_sched_data; + struct bfq_sched_data *sched_data; + + unsigned short ioprio, new_ioprio; + unsigned short ioprio_class, new_ioprio_class; + + int ioprio_changed; +}; + +struct bfq_group; + +/** + * struct bfq_queue - leaf schedulable entity. + * @ref: reference counter. + * @bfqd: parent bfq_data. + * @new_bfqq: shared bfq_queue if queue is cooperating with + * one or more other queues. + * @pos_node: request-position tree member (see bfq_data's @rq_pos_tree). + * @pos_root: request-position tree root (see bfq_data's @rq_pos_tree). + * @sort_list: sorted list of pending requests. + * @next_rq: if fifo isn't expired, next request to serve. + * @queued: nr of requests queued in @sort_list. + * @allocated: currently allocated requests. + * @meta_pending: pending metadata requests. + * @fifo: fifo list of requests in sort_list. + * @entity: entity representing this queue in the scheduler. + * @max_budget: maximum budget allowed from the feedback mechanism. + * @budget_timeout: budget expiration (in jiffies). + * @dispatched: number of requests on the dispatch list or inside driver. + * @flags: status flags. + * @bfqq_list: node for active/idle bfqq list inside our bfqd. + * @burst_list_node: node for the device's burst list. + * @seek_samples: number of seeks sampled + * @seek_total: sum of the distances of the seeks sampled + * @seek_mean: mean seek distance + * @last_request_pos: position of the last request enqueued + * @requests_within_timer: number of consecutive pairs of request completion + * and arrival, such that the queue becomes idle + * after the completion, but the next request arrives + * within an idle time slice; used only if the queue's + * IO_bound has been cleared. + * @pid: pid of the process owning the queue, used for logging purposes. + * @last_wr_start_finish: start time of the current weight-raising period if + * the @bfq-queue is being weight-raised, otherwise + * finish time of the last weight-raising period + * @wr_cur_max_time: current max raising time for this queue + * @soft_rt_next_start: minimum time instant such that, only if a new + * request is enqueued after this time instant in an + * idle @bfq_queue with no outstanding requests, then + * the task associated with the queue it is deemed as + * soft real-time (see the comments to the function + * bfq_bfqq_softrt_next_start()) + * @last_idle_bklogged: time of the last transition of the @bfq_queue from + * idle to backlogged + * @service_from_backlogged: cumulative service received from the @bfq_queue + * since the last transition from idle to + * backlogged + * @bic: pointer to the bfq_io_cq owning the bfq_queue, set to %NULL if the + * queue is shared + * + * A bfq_queue is a leaf request queue; it can be associated with an + * io_context or more, if it is async or shared between cooperating + * processes. @cgroup holds a reference to the cgroup, to be sure that it + * does not disappear while a bfqq still references it (mostly to avoid + * races between request issuing and task migration followed by cgroup + * destruction). + * All the fields are protected by the queue lock of the containing bfqd. + */ +struct bfq_queue { + atomic_t ref; + struct bfq_data *bfqd; + + /* fields for cooperating queues handling */ + struct bfq_queue *new_bfqq; + struct rb_node pos_node; + struct rb_root *pos_root; + + struct rb_root sort_list; + struct request *next_rq; + int queued[2]; + int allocated[2]; + int meta_pending; + struct list_head fifo; + + struct bfq_entity entity; + + unsigned long max_budget; + unsigned long budget_timeout; + + int dispatched; + + unsigned int flags; + + struct list_head bfqq_list; + + struct hlist_node burst_list_node; + + unsigned int seek_samples; + u64 seek_total; + sector_t seek_mean; + sector_t last_request_pos; + + unsigned int requests_within_timer; + + pid_t pid; + struct bfq_io_cq *bic; + + /* weight-raising fields */ + unsigned long wr_cur_max_time; + unsigned long soft_rt_next_start; + unsigned long last_wr_start_finish; + unsigned int wr_coeff; + unsigned long last_idle_bklogged; + unsigned long service_from_backlogged; +}; + +/** + * struct bfq_ttime - per process thinktime stats. + * @ttime_total: total process thinktime + * @ttime_samples: number of thinktime samples + * @ttime_mean: average process thinktime + */ +struct bfq_ttime { + unsigned long last_end_request; + + unsigned long ttime_total; + unsigned long ttime_samples; + unsigned long ttime_mean; +}; + +/** + * struct bfq_io_cq - per (request_queue, io_context) structure. + * @icq: associated io_cq structure + * @bfqq: array of two process queues, the sync and the async + * @ttime: associated @bfq_ttime struct + * @wr_time_left: snapshot of the time left before weight raising ends + * for the sync queue associated to this process; this + * snapshot is taken to remember this value while the weight + * raising is suspended because the queue is merged with a + * shared queue, and is used to set @raising_cur_max_time + * when the queue is split from the shared queue and its + * weight is raised again + * @saved_idle_window: same purpose as the previous field for the idle + * window + * @saved_IO_bound: same purpose as the previous two fields for the I/O + * bound classification of a queue + * @saved_in_large_burst: same purpose as the previous fields for the + * value of the field keeping the queue's belonging + * to a large burst + * @was_in_burst_list: true if the queue belonged to a burst list + * before its merge with another cooperating queue + * @cooperations: counter of consecutive successful queue merges underwent + * by any of the process' @bfq_queues + * @failed_cooperations: counter of consecutive failed queue merges of any + * of the process' @bfq_queues + */ +struct bfq_io_cq { + struct io_cq icq; /* must be the first member */ + struct bfq_queue *bfqq[2]; + struct bfq_ttime ttime; + + unsigned int wr_time_left; + bool saved_idle_window; + bool saved_IO_bound; + + bool saved_in_large_burst; + bool was_in_burst_list; + + unsigned int cooperations; + unsigned int failed_cooperations; +}; + +enum bfq_device_speed { + BFQ_BFQD_FAST, + BFQ_BFQD_SLOW, +}; + +/** + * struct bfq_data - per device data structure. + * @queue: request queue for the managed device. + * @root_group: root bfq_group for the device. + * @rq_pos_tree: rbtree sorted by next_request position, used when + * determining if two or more queues have interleaving + * requests (see bfq_close_cooperator()). + * @active_numerous_groups: number of bfq_groups containing more than one + * active @bfq_entity. + * @queue_weights_tree: rbtree of weight counters of @bfq_queues, sorted by + * weight. Used to keep track of whether all @bfq_queues + * have the same weight. The tree contains one counter + * for each distinct weight associated to some active + * and not weight-raised @bfq_queue (see the comments to + * the functions bfq_weights_tree_[add|remove] for + * further details). + * @group_weights_tree: rbtree of non-queue @bfq_entity weight counters, sorted + * by weight. Used to keep track of whether all + * @bfq_groups have the same weight. The tree contains + * one counter for each distinct weight associated to + * some active @bfq_group (see the comments to the + * functions bfq_weights_tree_[add|remove] for further + * details). + * @busy_queues: number of bfq_queues containing requests (including the + * queue in service, even if it is idling). + * @busy_in_flight_queues: number of @bfq_queues containing pending or + * in-flight requests, plus the @bfq_queue in + * service, even if idle but waiting for the + * possible arrival of its next sync request. This + * field is updated only if the device is rotational, + * but used only if the device is also NCQ-capable. + * The reason why the field is updated also for non- + * NCQ-capable rotational devices is related to the + * fact that the value of @hw_tag may be set also + * later than when busy_in_flight_queues may need to + * be incremented for the first time(s). Taking also + * this possibility into account, to avoid unbalanced + * increments/decrements, would imply more overhead + * than just updating busy_in_flight_queues + * regardless of the value of @hw_tag. + * @const_seeky_busy_in_flight_queues: number of constantly-seeky @bfq_queues + * (that is, seeky queues that expired + * for budget timeout at least once) + * containing pending or in-flight + * requests, including the in-service + * @bfq_queue if constantly seeky. This + * field is updated only if the device + * is rotational, but used only if the + * device is also NCQ-capable (see the + * comments to @busy_in_flight_queues). + * @wr_busy_queues: number of weight-raised busy @bfq_queues. + * @queued: number of queued requests. + * @rq_in_driver: number of requests dispatched and waiting for completion. + * @sync_flight: number of sync requests in the driver. + * @max_rq_in_driver: max number of reqs in driver in the last + * @hw_tag_samples completed requests. + * @hw_tag_samples: nr of samples used to calculate hw_tag. + * @hw_tag: flag set to one if the driver is showing a queueing behavior. + * @budgets_assigned: number of budgets assigned. + * @idle_slice_timer: timer set when idling for the next sequential request + * from the queue in service. + * @unplug_work: delayed work to restart dispatching on the request queue. + * @in_service_queue: bfq_queue in service. + * @in_service_bic: bfq_io_cq (bic) associated with the @in_service_queue. + * @last_position: on-disk position of the last served request. + * @last_budget_start: beginning of the last budget. + * @last_idling_start: beginning of the last idle slice. + * @peak_rate: peak transfer rate observed for a budget. + * @peak_rate_samples: number of samples used to calculate @peak_rate. + * @bfq_max_budget: maximum budget allotted to a bfq_queue before + * rescheduling. + * @group_list: list of all the bfq_groups active on the device. + * @active_list: list of all the bfq_queues active on the device. + * @idle_list: list of all the bfq_queues idle on the device. + * @bfq_quantum: max number of requests dispatched per dispatch round. + * @bfq_fifo_expire: timeout for async/sync requests; when it expires + * requests are served in fifo order. + * @bfq_back_penalty: weight of backward seeks wrt forward ones. + * @bfq_back_max: maximum allowed backward seek. + * @bfq_slice_idle: maximum idling time. + * @bfq_user_max_budget: user-configured max budget value + * (0 for auto-tuning). + * @bfq_max_budget_async_rq: maximum budget (in nr of requests) allotted to + * async queues. + * @bfq_timeout: timeout for bfq_queues to consume their budget; used to + * to prevent seeky queues to impose long latencies to well + * behaved ones (this also implies that seeky queues cannot + * receive guarantees in the service domain; after a timeout + * they are charged for the whole allocated budget, to try + * to preserve a behavior reasonably fair among them, but + * without service-domain guarantees). + * @bfq_coop_thresh: number of queue merges after which a @bfq_queue is + * no more granted any weight-raising. + * @bfq_failed_cooperations: number of consecutive failed cooperation + * chances after which weight-raising is restored + * to a queue subject to more than bfq_coop_thresh + * queue merges. + * @bfq_requests_within_timer: number of consecutive requests that must be + * issued within the idle time slice to set + * again idling to a queue which was marked as + * non-I/O-bound (see the definition of the + * IO_bound flag for further details). + * @last_ins_in_burst: last time at which a queue entered the current + * burst of queues being activated shortly after + * each other; for more details about this and the + * following parameters related to a burst of + * activations, see the comments to the function + * @bfq_handle_burst. + * @bfq_burst_interval: reference time interval used to decide whether a + * queue has been activated shortly after + * @last_ins_in_burst. + * @burst_size: number of queues in the current burst of queue activations. + * @bfq_large_burst_thresh: maximum burst size above which the current + * queue-activation burst is deemed as 'large'. + * @large_burst: true if a large queue-activation burst is in progress. + * @burst_list: head of the burst list (as for the above fields, more details + * in the comments to the function bfq_handle_burst). + * @low_latency: if set to true, low-latency heuristics are enabled. + * @bfq_wr_coeff: maximum factor by which the weight of a weight-raised + * queue is multiplied. + * @bfq_wr_max_time: maximum duration of a weight-raising period (jiffies). + * @bfq_wr_rt_max_time: maximum duration for soft real-time processes. + * @bfq_wr_min_idle_time: minimum idle period after which weight-raising + * may be reactivated for a queue (in jiffies). + * @bfq_wr_min_inter_arr_async: minimum period between request arrivals + * after which weight-raising may be + * reactivated for an already busy queue + * (in jiffies). + * @bfq_wr_max_softrt_rate: max service-rate for a soft real-time queue, + * sectors per seconds. + * @RT_prod: cached value of the product R*T used for computing the maximum + * duration of the weight raising automatically. + * @device_speed: device-speed class for the low-latency heuristic. + * @oom_bfqq: fallback dummy bfqq for extreme OOM conditions. + * + * All the fields are protected by the @queue lock. + */ +struct bfq_data { + struct request_queue *queue; + + struct bfq_group *root_group; + struct rb_root rq_pos_tree; + +#ifdef CONFIG_CGROUP_BFQIO + int active_numerous_groups; +#endif + + struct rb_root queue_weights_tree; + struct rb_root group_weights_tree; + + int busy_queues; + int busy_in_flight_queues; + int const_seeky_busy_in_flight_queues; + int wr_busy_queues; + int queued; + int rq_in_driver; + int sync_flight; + + int max_rq_in_driver; + int hw_tag_samples; + int hw_tag; + + int budgets_assigned; + + struct timer_list idle_slice_timer; + struct work_struct unplug_work; + + struct bfq_queue *in_service_queue; + struct bfq_io_cq *in_service_bic; + + sector_t last_position; + + ktime_t last_budget_start; + ktime_t last_idling_start; + int peak_rate_samples; + u64 peak_rate; + unsigned long bfq_max_budget; + + struct hlist_head group_list; + struct list_head active_list; + struct list_head idle_list; + + unsigned int bfq_quantum; + unsigned int bfq_fifo_expire[2]; + unsigned int bfq_back_penalty; + unsigned int bfq_back_max; + unsigned int bfq_slice_idle; + u64 bfq_class_idle_last_service; + + unsigned int bfq_user_max_budget; + unsigned int bfq_max_budget_async_rq; + unsigned int bfq_timeout[2]; + + unsigned int bfq_coop_thresh; + unsigned int bfq_failed_cooperations; + unsigned int bfq_requests_within_timer; + + unsigned long last_ins_in_burst; + unsigned long bfq_burst_interval; + int burst_size; + unsigned long bfq_large_burst_thresh; + bool large_burst; + struct hlist_head burst_list; + + bool low_latency; + + /* parameters of the low_latency heuristics */ + unsigned int bfq_wr_coeff; + unsigned int bfq_wr_max_time; + unsigned int bfq_wr_rt_max_time; + unsigned int bfq_wr_min_idle_time; + unsigned long bfq_wr_min_inter_arr_async; + unsigned int bfq_wr_max_softrt_rate; + u64 RT_prod; + enum bfq_device_speed device_speed; + + struct bfq_queue oom_bfqq; +}; + +enum bfqq_state_flags { + BFQ_BFQQ_FLAG_busy = 0, /* has requests or is in service */ + BFQ_BFQQ_FLAG_wait_request, /* waiting for a request */ + BFQ_BFQQ_FLAG_must_alloc, /* must be allowed rq alloc */ + BFQ_BFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */ + BFQ_BFQQ_FLAG_idle_window, /* slice idling enabled */ + BFQ_BFQQ_FLAG_prio_changed, /* task priority has changed */ + BFQ_BFQQ_FLAG_sync, /* synchronous queue */ + BFQ_BFQQ_FLAG_budget_new, /* no completion with this budget */ + BFQ_BFQQ_FLAG_IO_bound, /* + * bfqq has timed-out at least once + * having consumed at most 2/10 of + * its budget + */ + BFQ_BFQQ_FLAG_in_large_burst, /* + * bfqq activated in a large burst, + * see comments to bfq_handle_burst. + */ + BFQ_BFQQ_FLAG_constantly_seeky, /* + * bfqq has proved to be slow and + * seeky until budget timeout + */ + BFQ_BFQQ_FLAG_softrt_update, /* + * may need softrt-next-start + * update + */ + BFQ_BFQQ_FLAG_coop, /* bfqq is shared */ + BFQ_BFQQ_FLAG_split_coop, /* shared bfqq will be split */ + BFQ_BFQQ_FLAG_just_split, /* queue has just been split */ +}; + +#define BFQ_BFQQ_FNS(name) \ +static inline void bfq_mark_bfqq_##name(struct bfq_queue *bfqq) \ +{ \ + (bfqq)->flags |= (1 << BFQ_BFQQ_FLAG_##name); \ +} \ +static inline void bfq_clear_bfqq_##name(struct bfq_queue *bfqq) \ +{ \ + (bfqq)->flags &= ~(1 << BFQ_BFQQ_FLAG_##name); \ +} \ +static inline int bfq_bfqq_##name(const struct bfq_queue *bfqq) \ +{ \ + return ((bfqq)->flags & (1 << BFQ_BFQQ_FLAG_##name)) != 0; \ +} + +BFQ_BFQQ_FNS(busy); +BFQ_BFQQ_FNS(wait_request); +BFQ_BFQQ_FNS(must_alloc); +BFQ_BFQQ_FNS(fifo_expire); +BFQ_BFQQ_FNS(idle_window); +BFQ_BFQQ_FNS(prio_changed); +BFQ_BFQQ_FNS(sync); +BFQ_BFQQ_FNS(budget_new); +BFQ_BFQQ_FNS(IO_bound); +BFQ_BFQQ_FNS(in_large_burst); +BFQ_BFQQ_FNS(constantly_seeky); +BFQ_BFQQ_FNS(coop); +BFQ_BFQQ_FNS(split_coop); +BFQ_BFQQ_FNS(just_split); +BFQ_BFQQ_FNS(softrt_update); +#undef BFQ_BFQQ_FNS + +/* Logging facilities. */ +#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \ + blk_add_trace_msg((bfqd)->queue, "bfq%d " fmt, (bfqq)->pid, ##args) + +#define bfq_log(bfqd, fmt, args...) \ + blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args) + +/* Expiration reasons. */ +enum bfqq_expiration { + BFQ_BFQQ_TOO_IDLE = 0, /* + * queue has been idling for + * too long + */ + BFQ_BFQQ_BUDGET_TIMEOUT, /* budget took too long to be used */ + BFQ_BFQQ_BUDGET_EXHAUSTED, /* budget consumed */ + BFQ_BFQQ_NO_MORE_REQUESTS, /* the queue has no more requests */ +}; + +#ifdef CONFIG_CGROUP_BFQIO +/** + * struct bfq_group - per (device, cgroup) data structure. + * @entity: schedulable entity to insert into the parent group sched_data. + * @sched_data: own sched_data, to contain child entities (they may be + * both bfq_queues and bfq_groups). + * @group_node: node to be inserted into the bfqio_cgroup->group_data + * list of the containing cgroup's bfqio_cgroup. + * @bfqd_node: node to be inserted into the @bfqd->group_list list + * of the groups active on the same device; used for cleanup. + * @bfqd: the bfq_data for the device this group acts upon. + * @async_bfqq: array of async queues for all the tasks belonging to + * the group, one queue per ioprio value per ioprio_class, + * except for the idle class that has only one queue. + * @async_idle_bfqq: async queue for the idle class (ioprio is ignored). + * @my_entity: pointer to @entity, %NULL for the toplevel group; used + * to avoid too many special cases during group creation/ + * migration. + * @active_entities: number of active entities belonging to the group; + * unused for the root group. Used to know whether there + * are groups with more than one active @bfq_entity + * (see the comments to the function + * bfq_bfqq_must_not_expire()). + * + * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup + * there is a set of bfq_groups, each one collecting the lower-level + * entities belonging to the group that are acting on the same device. + * + * Locking works as follows: + * o @group_node is protected by the bfqio_cgroup lock, and is accessed + * via RCU from its readers. + * o @bfqd is protected by the queue lock, RCU is used to access it + * from the readers. + * o All the other fields are protected by the @bfqd queue lock. + */ +struct bfq_group { + struct bfq_entity entity; + struct bfq_sched_data sched_data; + + struct hlist_node group_node; + struct hlist_node bfqd_node; + + void *bfqd; + + struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR]; + struct bfq_queue *async_idle_bfqq; + + struct bfq_entity *my_entity; + + int active_entities; +}; + +/** + * struct bfqio_cgroup - bfq cgroup data structure. + * @css: subsystem state for bfq in the containing cgroup. + * @weight: cgroup weight. + * @ioprio: cgroup ioprio. + * @ioprio_class: cgroup ioprio_class. + * @lock: spinlock that protects @ioprio, @ioprio_class and @group_data. + * @group_data: list containing the bfq_group belonging to this cgroup. + * + * @group_data is accessed using RCU, with @lock protecting the updates, + * @ioprio and @ioprio_class are protected by @lock. + */ +struct bfqio_cgroup { + struct cgroup_subsys_state css; + + unsigned short weight, ioprio, ioprio_class; + + spinlock_t lock; + struct hlist_head group_data; +}; +#else +struct bfq_group { + struct bfq_sched_data sched_data; + + struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR]; + struct bfq_queue *async_idle_bfqq; +}; +#endif + +static inline struct bfq_service_tree * +bfq_entity_service_tree(struct bfq_entity *entity) +{ + struct bfq_sched_data *sched_data = entity->sched_data; + unsigned int idx = entity->ioprio_class - 1; + + BUG_ON(idx >= BFQ_IOPRIO_CLASSES); + BUG_ON(sched_data == NULL); + + return sched_data->service_tree + idx; +} + +static inline struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, + bool is_sync) +{ + return bic->bfqq[is_sync]; +} + +static inline void bic_set_bfqq(struct bfq_io_cq *bic, + struct bfq_queue *bfqq, bool is_sync) +{ + bic->bfqq[is_sync] = bfqq; +} + +static inline struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic) +{ + return bic->icq.q->elevator->elevator_data; +} + +/** + * bfq_get_bfqd_locked - get a lock to a bfqd using a RCU protected pointer. + * @ptr: a pointer to a bfqd. + * @flags: storage for the flags to be saved. + * + * This function allows bfqg->bfqd to be protected by the + * queue lock of the bfqd they reference; the pointer is dereferenced + * under RCU, so the storage for bfqd is assured to be safe as long + * as the RCU read side critical section does not end. After the + * bfqd->queue->queue_lock is taken the pointer is rechecked, to be + * sure that no other writer accessed it. If we raced with a writer, + * the function returns NULL, with the queue unlocked, otherwise it + * returns the dereferenced pointer, with the queue locked. + */ +static inline struct bfq_data *bfq_get_bfqd_locked(void **ptr, + unsigned long *flags) +{ + struct bfq_data *bfqd; + + rcu_read_lock(); + bfqd = rcu_dereference(*(struct bfq_data **)ptr); + + if (bfqd != NULL) { + spin_lock_irqsave(bfqd->queue->queue_lock, *flags); + if (*ptr == bfqd) + goto out; + spin_unlock_irqrestore(bfqd->queue->queue_lock, *flags); + } + + bfqd = NULL; +out: + rcu_read_unlock(); + return bfqd; +} + +static inline void bfq_put_bfqd_unlock(struct bfq_data *bfqd, + unsigned long *flags) +{ + spin_unlock_irqrestore(bfqd->queue->queue_lock, *flags); +} + +static void bfq_changed_ioprio(struct io_context *ioc, + struct bfq_io_cq *bic); +static void bfq_put_queue(struct bfq_queue *bfqq); +static void bfq_dispatch_insert(struct request_queue *q, struct request *rq); +static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd, + struct bfq_group *bfqg, int is_sync, + struct io_context *ioc, gfp_t gfp_mask); +static void bfq_end_wr_async_queues(struct bfq_data *bfqd, + struct bfq_group *bfqg); +static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg); +static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq); + +#endif /* _BFQ_H */ diff --git a/block/fiops-iosched.c b/block/fiops-iosched.c new file mode 100644 index 0000000..671b1d3 --- /dev/null +++ b/block/fiops-iosched.c @@ -0,0 +1,753 @@ +/* + * IOPS based IO scheduler. Based on CFQ. + * Copyright (C) 2003 Jens Axboe + * Shaohua Li + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include "blk.h" + +#define VIOS_SCALE_SHIFT 10 +#define VIOS_SCALE (1 << VIOS_SCALE_SHIFT) + +#define VIOS_READ_SCALE (1) +#define VIOS_WRITE_SCALE (1) +#define VIOS_SYNC_SCALE (2) +#define VIOS_ASYNC_SCALE (5) + +#define VIOS_PRIO_SCALE (5) + +struct fiops_rb_root { + struct rb_root rb; + struct rb_node *left; + unsigned count; + + u64 min_vios; +}; +#define FIOPS_RB_ROOT (struct fiops_rb_root) { .rb = RB_ROOT} + +enum wl_prio_t { + IDLE_WORKLOAD = 0, + BE_WORKLOAD = 1, + RT_WORKLOAD = 2, + FIOPS_PRIO_NR, +}; + +struct fiops_data { + struct request_queue *queue; + + struct fiops_rb_root service_tree[FIOPS_PRIO_NR]; + + unsigned int busy_queues; + unsigned int in_flight[2]; + + struct work_struct unplug_work; + + unsigned int read_scale; + unsigned int write_scale; + unsigned int sync_scale; + unsigned int async_scale; +}; + +struct fiops_ioc { + struct io_cq icq; + + unsigned int flags; + struct fiops_data *fiopsd; + struct rb_node rb_node; + u64 vios; /* key in service_tree */ + struct fiops_rb_root *service_tree; + + unsigned int in_flight; + + struct rb_root sort_list; + struct list_head fifo; + + pid_t pid; + unsigned short ioprio; + enum wl_prio_t wl_type; +}; + +#define ioc_service_tree(ioc) (&((ioc)->fiopsd->service_tree[(ioc)->wl_type])) +#define RQ_CIC(rq) icq_to_cic((rq)->elv.icq) + +enum ioc_state_flags { + FIOPS_IOC_FLAG_on_rr = 0, /* on round-robin busy list */ + FIOPS_IOC_FLAG_prio_changed, /* task priority has changed */ +}; + +#define FIOPS_IOC_FNS(name) \ +static inline void fiops_mark_ioc_##name(struct fiops_ioc *ioc) \ +{ \ + ioc->flags |= (1 << FIOPS_IOC_FLAG_##name); \ +} \ +static inline void fiops_clear_ioc_##name(struct fiops_ioc *ioc) \ +{ \ + ioc->flags &= ~(1 << FIOPS_IOC_FLAG_##name); \ +} \ +static inline int fiops_ioc_##name(const struct fiops_ioc *ioc) \ +{ \ + return ((ioc)->flags & (1 << FIOPS_IOC_FLAG_##name)) != 0; \ +} + +FIOPS_IOC_FNS(on_rr); +FIOPS_IOC_FNS(prio_changed); +#undef FIOPS_IOC_FNS + +#define fiops_log_ioc(fiopsd, ioc, fmt, args...) \ + blk_add_trace_msg((fiopsd)->queue, "ioc%d " fmt, (ioc)->pid, ##args) +#define fiops_log(fiopsd, fmt, args...) \ + blk_add_trace_msg((fiopsd)->queue, "fiops " fmt, ##args) + +enum wl_prio_t fiops_wl_type(short prio_class) +{ + if (prio_class == IOPRIO_CLASS_RT) + return RT_WORKLOAD; + if (prio_class == IOPRIO_CLASS_BE) + return BE_WORKLOAD; + return IDLE_WORKLOAD; +} + +static inline struct fiops_ioc *icq_to_cic(struct io_cq *icq) +{ + /* cic->icq is the first member, %NULL will convert to %NULL */ + return container_of(icq, struct fiops_ioc, icq); +} + +static inline struct fiops_ioc *fiops_cic_lookup(struct fiops_data *fiopsd, + struct io_context *ioc) +{ + if (ioc) + return icq_to_cic(ioc_lookup_icq(ioc, fiopsd->queue)); + return NULL; +} + +/* + * The below is leftmost cache rbtree addon + */ +static struct fiops_ioc *fiops_rb_first(struct fiops_rb_root *root) +{ + /* Service tree is empty */ + if (!root->count) + return NULL; + + if (!root->left) + root->left = rb_first(&root->rb); + + if (root->left) + return rb_entry(root->left, struct fiops_ioc, rb_node); + + return NULL; +} + +static void rb_erase_init(struct rb_node *n, struct rb_root *root) +{ + rb_erase(n, root); + RB_CLEAR_NODE(n); +} + +static void fiops_rb_erase(struct rb_node *n, struct fiops_rb_root *root) +{ + if (root->left == n) + root->left = NULL; + rb_erase_init(n, &root->rb); + --root->count; +} + +static inline u64 max_vios(u64 min_vios, u64 vios) +{ + s64 delta = (s64)(vios - min_vios); + if (delta > 0) + min_vios = vios; + + return min_vios; +} + +static void fiops_update_min_vios(struct fiops_rb_root *service_tree) +{ + struct fiops_ioc *ioc; + + ioc = fiops_rb_first(service_tree); + if (!ioc) + return; + service_tree->min_vios = max_vios(service_tree->min_vios, ioc->vios); +} + +/* + * The fiopsd->service_trees holds all pending fiops_ioc's that have + * requests waiting to be processed. It is sorted in the order that + * we will service the queues. + */ +static void fiops_service_tree_add(struct fiops_data *fiopsd, + struct fiops_ioc *ioc) +{ + struct rb_node **p, *parent; + struct fiops_ioc *__ioc; + struct fiops_rb_root *service_tree = ioc_service_tree(ioc); + u64 vios; + int left; + + /* New added IOC */ + if (RB_EMPTY_NODE(&ioc->rb_node)) { + if (ioc->in_flight > 0) + vios = ioc->vios; + else + vios = max_vios(service_tree->min_vios, ioc->vios); + } else { + vios = ioc->vios; + /* ioc->service_tree might not equal to service_tree */ + fiops_rb_erase(&ioc->rb_node, ioc->service_tree); + ioc->service_tree = NULL; + } + + fiops_log_ioc(fiopsd, ioc, "service tree add, vios %lld", vios); + + left = 1; + parent = NULL; + ioc->service_tree = service_tree; + p = &service_tree->rb.rb_node; + while (*p) { + struct rb_node **n; + + parent = *p; + __ioc = rb_entry(parent, struct fiops_ioc, rb_node); + + /* + * sort by key, that represents service time. + */ + if (vios < __ioc->vios) + n = &(*p)->rb_left; + else { + n = &(*p)->rb_right; + left = 0; + } + + p = n; + } + + if (left) + service_tree->left = &ioc->rb_node; + + ioc->vios = vios; + rb_link_node(&ioc->rb_node, parent, p); + rb_insert_color(&ioc->rb_node, &service_tree->rb); + service_tree->count++; + + fiops_update_min_vios(service_tree); +} + +/* + * Update ioc's position in the service tree. + */ +static void fiops_resort_rr_list(struct fiops_data *fiopsd, + struct fiops_ioc *ioc) +{ + /* + * Resorting requires the ioc to be on the RR list already. + */ + if (fiops_ioc_on_rr(ioc)) + fiops_service_tree_add(fiopsd, ioc); +} + +/* + * add to busy list of queues for service, trying to be fair in ordering + * the pending list according to last request service + */ +static void fiops_add_ioc_rr(struct fiops_data *fiopsd, struct fiops_ioc *ioc) +{ + BUG_ON(fiops_ioc_on_rr(ioc)); + fiops_mark_ioc_on_rr(ioc); + + fiopsd->busy_queues++; + + fiops_resort_rr_list(fiopsd, ioc); +} + +/* + * Called when the ioc no longer has requests pending, remove it from + * the service tree. + */ +static void fiops_del_ioc_rr(struct fiops_data *fiopsd, struct fiops_ioc *ioc) +{ + BUG_ON(!fiops_ioc_on_rr(ioc)); + fiops_clear_ioc_on_rr(ioc); + + if (!RB_EMPTY_NODE(&ioc->rb_node)) { + fiops_rb_erase(&ioc->rb_node, ioc->service_tree); + ioc->service_tree = NULL; + } + + BUG_ON(!fiopsd->busy_queues); + fiopsd->busy_queues--; +} + +/* + * rb tree support functions + */ +static void fiops_del_rq_rb(struct request *rq) +{ + struct fiops_ioc *ioc = RQ_CIC(rq); + + elv_rb_del(&ioc->sort_list, rq); +} + +static void fiops_add_rq_rb(struct request *rq) +{ + struct fiops_ioc *ioc = RQ_CIC(rq); + struct fiops_data *fiopsd = ioc->fiopsd; + + elv_rb_add(&ioc->sort_list, rq); + + if (!fiops_ioc_on_rr(ioc)) + fiops_add_ioc_rr(fiopsd, ioc); +} + +static void fiops_reposition_rq_rb(struct fiops_ioc *ioc, struct request *rq) +{ + elv_rb_del(&ioc->sort_list, rq); + fiops_add_rq_rb(rq); +} + +static void fiops_remove_request(struct request *rq) +{ + list_del_init(&rq->queuelist); + fiops_del_rq_rb(rq); +} + +static u64 fiops_scaled_vios(struct fiops_data *fiopsd, + struct fiops_ioc *ioc, struct request *rq) +{ + int vios = VIOS_SCALE; + + if (rq_data_dir(rq) == WRITE) + vios = vios * fiopsd->write_scale / fiopsd->read_scale; + + if (!rq_is_sync(rq)) + vios = vios * fiopsd->async_scale / fiopsd->sync_scale; + + vios += vios * (ioc->ioprio - IOPRIO_NORM) / VIOS_PRIO_SCALE; + + return vios; +} + +/* return vios dispatched */ +static u64 fiops_dispatch_request(struct fiops_data *fiopsd, + struct fiops_ioc *ioc) +{ + struct request *rq; + struct request_queue *q = fiopsd->queue; + + rq = rq_entry_fifo(ioc->fifo.next); + + fiops_remove_request(rq); + elv_dispatch_add_tail(q, rq); + + fiopsd->in_flight[rq_is_sync(rq)]++; + ioc->in_flight++; + + return fiops_scaled_vios(fiopsd, ioc, rq); +} + +static int fiops_forced_dispatch(struct fiops_data *fiopsd) +{ + struct fiops_ioc *ioc; + int dispatched = 0; + int i; + + for (i = RT_WORKLOAD; i >= IDLE_WORKLOAD; i--) { + while (!RB_EMPTY_ROOT(&fiopsd->service_tree[i].rb)) { + ioc = fiops_rb_first(&fiopsd->service_tree[i]); + + while (!list_empty(&ioc->fifo)) { + fiops_dispatch_request(fiopsd, ioc); + dispatched++; + } + if (fiops_ioc_on_rr(ioc)) + fiops_del_ioc_rr(fiopsd, ioc); + } + } + return dispatched; +} + +static struct fiops_ioc *fiops_select_ioc(struct fiops_data *fiopsd) +{ + struct fiops_ioc *ioc; + struct fiops_rb_root *service_tree = NULL; + int i; + struct request *rq; + + for (i = RT_WORKLOAD; i >= IDLE_WORKLOAD; i--) { + if (!RB_EMPTY_ROOT(&fiopsd->service_tree[i].rb)) { + service_tree = &fiopsd->service_tree[i]; + break; + } + } + + if (!service_tree) + return NULL; + + ioc = fiops_rb_first(service_tree); + + rq = rq_entry_fifo(ioc->fifo.next); + /* + * we are the only async task and sync requests are in flight, delay a + * moment. If there are other tasks coming, sync tasks have no chance + * to be starved, don't delay + */ + if (!rq_is_sync(rq) && fiopsd->in_flight[1] != 0 && + service_tree->count == 1) { + fiops_log_ioc(fiopsd, ioc, + "postpone async, in_flight async %d sync %d", + fiopsd->in_flight[0], fiopsd->in_flight[1]); + return NULL; + } + + return ioc; +} + +static void fiops_charge_vios(struct fiops_data *fiopsd, + struct fiops_ioc *ioc, u64 vios) +{ + struct fiops_rb_root *service_tree = ioc->service_tree; + ioc->vios += vios; + + fiops_log_ioc(fiopsd, ioc, "charge vios %lld, new vios %lld", vios, ioc->vios); + + if (RB_EMPTY_ROOT(&ioc->sort_list)) + fiops_del_ioc_rr(fiopsd, ioc); + else + fiops_resort_rr_list(fiopsd, ioc); + + fiops_update_min_vios(service_tree); +} + +static int fiops_dispatch_requests(struct request_queue *q, int force) +{ + struct fiops_data *fiopsd = q->elevator->elevator_data; + struct fiops_ioc *ioc; + u64 vios; + + if (unlikely(force)) + return fiops_forced_dispatch(fiopsd); + + ioc = fiops_select_ioc(fiopsd); + if (!ioc) + return 0; + + vios = fiops_dispatch_request(fiopsd, ioc); + + fiops_charge_vios(fiopsd, ioc, vios); + return 1; +} + +static void fiops_init_prio_data(struct fiops_ioc *cic) +{ + struct task_struct *tsk = current; + struct io_context *ioc = cic->icq.ioc; + int ioprio_class; + + if (!fiops_ioc_prio_changed(cic)) + return; + + ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio); + switch (ioprio_class) { + default: + printk(KERN_ERR "fiops: bad prio %x\n", ioprio_class); + case IOPRIO_CLASS_NONE: + /* + * no prio set, inherit CPU scheduling settings + */ + cic->ioprio = task_nice_ioprio(tsk); + cic->wl_type = fiops_wl_type(task_nice_ioclass(tsk)); + break; + case IOPRIO_CLASS_RT: + cic->ioprio = task_ioprio(ioc); + cic->wl_type = fiops_wl_type(IOPRIO_CLASS_RT); + break; + case IOPRIO_CLASS_BE: + cic->ioprio = task_ioprio(ioc); + cic->wl_type = fiops_wl_type(IOPRIO_CLASS_BE); + break; + case IOPRIO_CLASS_IDLE: + cic->wl_type = fiops_wl_type(IOPRIO_CLASS_IDLE); + cic->ioprio = 7; + break; + } + + fiops_clear_ioc_prio_changed(cic); +} + +static void fiops_insert_request(struct request_queue *q, struct request *rq) +{ + struct fiops_ioc *ioc = RQ_CIC(rq); + + fiops_init_prio_data(ioc); + + list_add_tail(&rq->queuelist, &ioc->fifo); + + fiops_add_rq_rb(rq); +} + +/* + * scheduler run of queue, if there are requests pending and no one in the + * driver that will restart queueing + */ +static inline void fiops_schedule_dispatch(struct fiops_data *fiopsd) +{ + if (fiopsd->busy_queues) + kblockd_schedule_work(fiopsd->queue, &fiopsd->unplug_work); +} + +static void fiops_completed_request(struct request_queue *q, struct request *rq) +{ + struct fiops_data *fiopsd = q->elevator->elevator_data; + struct fiops_ioc *ioc = RQ_CIC(rq); + + fiopsd->in_flight[rq_is_sync(rq)]--; + ioc->in_flight--; + + fiops_log_ioc(fiopsd, ioc, "in_flight %d, busy queues %d", + ioc->in_flight, fiopsd->busy_queues); + + if (fiopsd->in_flight[0] + fiopsd->in_flight[1] == 0) + fiops_schedule_dispatch(fiopsd); +} + +static struct request * +fiops_find_rq_fmerge(struct fiops_data *fiopsd, struct bio *bio) +{ + struct task_struct *tsk = current; + struct fiops_ioc *cic; + + cic = fiops_cic_lookup(fiopsd, tsk->io_context); + + if (cic) { + sector_t sector = bio->bi_sector + bio_sectors(bio); + + return elv_rb_find(&cic->sort_list, sector); + } + + return NULL; +} + +static int fiops_merge(struct request_queue *q, struct request **req, + struct bio *bio) +{ + struct fiops_data *fiopsd = q->elevator->elevator_data; + struct request *__rq; + + __rq = fiops_find_rq_fmerge(fiopsd, bio); + if (__rq && elv_rq_merge_ok(__rq, bio)) { + *req = __rq; + return ELEVATOR_FRONT_MERGE; + } + + return ELEVATOR_NO_MERGE; +} + +static void fiops_merged_request(struct request_queue *q, struct request *req, + int type) +{ + if (type == ELEVATOR_FRONT_MERGE) { + struct fiops_ioc *ioc = RQ_CIC(req); + + fiops_reposition_rq_rb(ioc, req); + } +} + +static void +fiops_merged_requests(struct request_queue *q, struct request *rq, + struct request *next) +{ + struct fiops_ioc *ioc = RQ_CIC(rq); + struct fiops_data *fiopsd = q->elevator->elevator_data; + + fiops_remove_request(next); + + ioc = RQ_CIC(next); + /* + * all requests of this task are merged to other tasks, delete it + * from the service tree. + */ + if (fiops_ioc_on_rr(ioc) && RB_EMPTY_ROOT(&ioc->sort_list)) + fiops_del_ioc_rr(fiopsd, ioc); +} + +static int fiops_allow_merge(struct request_queue *q, struct request *rq, + struct bio *bio) +{ + struct fiops_data *fiopsd = q->elevator->elevator_data; + struct fiops_ioc *cic; + + /* + * Lookup the ioc that this bio will be queued with. Allow + * merge only if rq is queued there. + */ + cic = fiops_cic_lookup(fiopsd, current->io_context); + + return cic == RQ_CIC(rq); +} + +static void fiops_exit_queue(struct elevator_queue *e) +{ + struct fiops_data *fiopsd = e->elevator_data; + + cancel_work_sync(&fiopsd->unplug_work); + + kfree(fiopsd); +} + +static void fiops_kick_queue(struct work_struct *work) +{ + struct fiops_data *fiopsd = + container_of(work, struct fiops_data, unplug_work); + struct request_queue *q = fiopsd->queue; + + spin_lock_irq(q->queue_lock); + __blk_run_queue(q); + spin_unlock_irq(q->queue_lock); +} + +static void *fiops_init_queue(struct request_queue *q) +{ + struct fiops_data *fiopsd; + int i; + + fiopsd = kzalloc_node(sizeof(*fiopsd), GFP_KERNEL, q->node); + if (!fiopsd) + return NULL; + + fiopsd->queue = q; + + for (i = IDLE_WORKLOAD; i <= RT_WORKLOAD; i++) + fiopsd->service_tree[i] = FIOPS_RB_ROOT; + + INIT_WORK(&fiopsd->unplug_work, fiops_kick_queue); + + fiopsd->read_scale = VIOS_READ_SCALE; + fiopsd->write_scale = VIOS_WRITE_SCALE; + fiopsd->sync_scale = VIOS_SYNC_SCALE; + fiopsd->async_scale = VIOS_ASYNC_SCALE; + + return fiopsd; +} + +static void fiops_init_icq(struct io_cq *icq) +{ + struct fiops_data *fiopsd = icq->q->elevator->elevator_data; + struct fiops_ioc *ioc = icq_to_cic(icq); + + RB_CLEAR_NODE(&ioc->rb_node); + INIT_LIST_HEAD(&ioc->fifo); + ioc->sort_list = RB_ROOT; + + ioc->fiopsd = fiopsd; + + ioc->pid = current->pid; + fiops_mark_ioc_prio_changed(ioc); +} + +/* + * sysfs parts below --> + */ +static ssize_t +fiops_var_show(unsigned int var, char *page) +{ + return sprintf(page, "%d\n", var); +} + +static ssize_t +fiops_var_store(unsigned int *var, const char *page, size_t count) +{ + char *p = (char *) page; + + *var = simple_strtoul(p, &p, 10); + return count; +} + +#define SHOW_FUNCTION(__FUNC, __VAR) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct fiops_data *fiopsd = e->elevator_data; \ + return fiops_var_show(__VAR, (page)); \ +} +SHOW_FUNCTION(fiops_read_scale_show, fiopsd->read_scale); +SHOW_FUNCTION(fiops_write_scale_show, fiopsd->write_scale); +SHOW_FUNCTION(fiops_sync_scale_show, fiopsd->sync_scale); +SHOW_FUNCTION(fiops_async_scale_show, fiopsd->async_scale); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct fiops_data *fiopsd = e->elevator_data; \ + unsigned int __data; \ + int ret = fiops_var_store(&__data, (page), count); \ + if (__data < (MIN)) \ + __data = (MIN); \ + else if (__data > (MAX)) \ + __data = (MAX); \ + *(__PTR) = __data; \ + return ret; \ +} +STORE_FUNCTION(fiops_read_scale_store, &fiopsd->read_scale, 1, 100); +STORE_FUNCTION(fiops_write_scale_store, &fiopsd->write_scale, 1, 100); +STORE_FUNCTION(fiops_sync_scale_store, &fiopsd->sync_scale, 1, 100); +STORE_FUNCTION(fiops_async_scale_store, &fiopsd->async_scale, 1, 100); +#undef STORE_FUNCTION + +#define FIOPS_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, fiops_##name##_show, fiops_##name##_store) + +static struct elv_fs_entry fiops_attrs[] = { + FIOPS_ATTR(read_scale), + FIOPS_ATTR(write_scale), + FIOPS_ATTR(sync_scale), + FIOPS_ATTR(async_scale), + __ATTR_NULL +}; + +static struct elevator_type iosched_fiops = { + .ops = { + .elevator_merge_fn = fiops_merge, + .elevator_merged_fn = fiops_merged_request, + .elevator_merge_req_fn = fiops_merged_requests, + .elevator_allow_merge_fn = fiops_allow_merge, + .elevator_dispatch_fn = fiops_dispatch_requests, + .elevator_add_req_fn = fiops_insert_request, + .elevator_completed_req_fn = fiops_completed_request, + .elevator_former_req_fn = elv_rb_former_request, + .elevator_latter_req_fn = elv_rb_latter_request, + .elevator_init_icq_fn = fiops_init_icq, + .elevator_init_fn = fiops_init_queue, + .elevator_exit_fn = fiops_exit_queue, + }, + .icq_size = sizeof(struct fiops_ioc), + .icq_align = __alignof__(struct fiops_ioc), + .elevator_attrs = fiops_attrs, + .elevator_name = "fiops", + .elevator_owner = THIS_MODULE, +}; + +static int __init fiops_init(void) +{ + return elv_register(&iosched_fiops); +} + +static void __exit fiops_exit(void) +{ + elv_unregister(&iosched_fiops); +} + +module_init(fiops_init); +module_exit(fiops_exit); + +MODULE_AUTHOR("Jens Axboe, Shaohua Li "); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("IOPS based IO scheduler"); diff --git a/block/sio-iosched.c b/block/sio-iosched.c new file mode 100644 index 0000000..3661a9a --- /dev/null +++ b/block/sio-iosched.c @@ -0,0 +1,403 @@ +/* + * Simple IO scheduler + * Based on Noop, Deadline and V(R) IO schedulers. + * + * Copyright (C) 2012 Miguel Boton + * + * + * This algorithm does not do any kind of sorting, as it is aimed for + * aleatory access devices, but it does some basic merging. We try to + * keep minimum overhead to achieve low latency. + * + * Asynchronous and synchronous requests are not treated separately, but + * we relay on deadlines to ensure fairness. + * + */ +#include +#include +#include +#include +#include +#include + +enum { ASYNC, SYNC }; + +/* Tunables */ +static const int sync_read_expire = HZ / 2; /* max time before a sync read is submitted. */ +static const int sync_write_expire = 2 * HZ; /* max time before a sync write is submitted. */ + +static const int async_read_expire = 4 * HZ; /* ditto for async, these limits are SOFT! */ +static const int async_write_expire = 16 * HZ; /* ditto for async, these limits are SOFT! */ + +static const int writes_starved = 2; /* max times reads can starve a write */ +static const int fifo_batch = 8; /* # of sequential requests treated as one + by the above parameters. For throughput. */ + +/* Elevator data */ +struct sio_data { + /* Request queues */ + struct list_head fifo_list[2][2]; + + /* Attributes */ + unsigned int batched; + unsigned int starved; + + /* Settings */ + int fifo_expire[2][2]; + int fifo_batch; + int writes_starved; +}; + +static void +sio_merged_requests(struct request_queue *q, struct request *rq, + struct request *next) +{ + /* + * If next expires before rq, assign its expire time to rq + * and move into next position (next will be deleted) in fifo. + */ + if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) { + if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) { + list_move(&rq->queuelist, &next->queuelist); + rq_set_fifo_time(rq, rq_fifo_time(next)); + } + } + + /* Delete next request */ + rq_fifo_clear(next); +} + +static void +sio_add_request(struct request_queue *q, struct request *rq) +{ + struct sio_data *sd = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + /* + * Add request to the proper fifo list and set its + * expire time. + */ + rq_set_fifo_time(rq, jiffies + sd->fifo_expire[sync][data_dir]); + list_add_tail(&rq->queuelist, &sd->fifo_list[sync][data_dir]); +} + +#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38) +static int +sio_queue_empty(struct request_queue *q) +{ + struct sio_data *sd = q->elevator->elevator_data; + + /* Check if fifo lists are empty */ + return list_empty(&sd->fifo_list[SYNC][READ]) && list_empty(&sd->fifo_list[SYNC][WRITE]) && + list_empty(&sd->fifo_list[ASYNC][READ]) && list_empty(&sd->fifo_list[ASYNC][WRITE]); +} +#endif + +static struct request * +sio_expired_request(struct sio_data *sd, int sync, int data_dir) +{ + struct list_head *list = &sd->fifo_list[sync][data_dir]; + struct request *rq; + + if (list_empty(list)) + return NULL; + + /* Retrieve request */ + rq = rq_entry_fifo(list->next); + + /* Request has expired */ + if (time_after(jiffies, rq_fifo_time(rq))) + return rq; + + return NULL; +} + +static struct request * +sio_choose_expired_request(struct sio_data *sd) +{ + struct request *rq; + + /* + * Check expired requests. + * Asynchronous requests have priority over synchronous. + * Write requests have priority over read. + */ + rq = sio_expired_request(sd, ASYNC, WRITE); + if (rq) + return rq; + rq = sio_expired_request(sd, ASYNC, READ); + if (rq) + return rq; + + rq = sio_expired_request(sd, SYNC, WRITE); + if (rq) + return rq; + rq = sio_expired_request(sd, SYNC, READ); + if (rq) + return rq; + + return NULL; +} + +static struct request * +sio_choose_request(struct sio_data *sd, int data_dir) +{ + struct list_head *sync = sd->fifo_list[SYNC]; + struct list_head *async = sd->fifo_list[ASYNC]; + + /* + * Retrieve request from available fifo list. + * Synchronous requests have priority over asynchronous. + * Read requests have priority over write. + */ + if (!list_empty(&sync[data_dir])) + return rq_entry_fifo(sync[data_dir].next); + if (!list_empty(&async[data_dir])) + return rq_entry_fifo(async[data_dir].next); + + if (!list_empty(&sync[!data_dir])) + return rq_entry_fifo(sync[!data_dir].next); + if (!list_empty(&async[!data_dir])) + return rq_entry_fifo(async[!data_dir].next); + + return NULL; +} + +static inline void +sio_dispatch_request(struct sio_data *sd, struct request *rq) +{ + /* + * Remove the request from the fifo list + * and dispatch it. + */ + rq_fifo_clear(rq); + elv_dispatch_add_tail(rq->q, rq); + + sd->batched++; + + if (rq_data_dir(rq)) + sd->starved = 0; + else + sd->starved++; +} + +static int +sio_dispatch_requests(struct request_queue *q, int force) +{ + struct sio_data *sd = q->elevator->elevator_data; + struct request *rq = NULL; + int data_dir = READ; + + /* + * Retrieve any expired request after a batch of + * sequential requests. + */ + if (sd->batched > sd->fifo_batch) { + sd->batched = 0; + rq = sio_choose_expired_request(sd); + } + + /* Retrieve request */ + if (!rq) { + if (sd->starved > sd->writes_starved) + data_dir = WRITE; + + rq = sio_choose_request(sd, data_dir); + if (!rq) + return 0; + } + + /* Dispatch request */ + sio_dispatch_request(sd, rq); + + return 1; +} + +static struct request * +sio_former_request(struct request_queue *q, struct request *rq) +{ + struct sio_data *sd = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + if (rq->queuelist.prev == &sd->fifo_list[sync][data_dir]) + return NULL; + + /* Return former request */ + return list_entry(rq->queuelist.prev, struct request, queuelist); +} + +static struct request * +sio_latter_request(struct request_queue *q, struct request *rq) +{ + struct sio_data *sd = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + if (rq->queuelist.next == &sd->fifo_list[sync][data_dir]) + return NULL; + + /* Return latter request */ + return list_entry(rq->queuelist.next, struct request, queuelist); +} + +static void * +sio_init_queue(struct request_queue *q) +{ + struct sio_data *sd; + + /* Allocate structure */ + sd = kmalloc_node(sizeof(*sd), GFP_KERNEL, q->node); + if (!sd) + return NULL; + + /* Initialize fifo lists */ + INIT_LIST_HEAD(&sd->fifo_list[SYNC][READ]); + INIT_LIST_HEAD(&sd->fifo_list[SYNC][WRITE]); + INIT_LIST_HEAD(&sd->fifo_list[ASYNC][READ]); + INIT_LIST_HEAD(&sd->fifo_list[ASYNC][WRITE]); + + /* Initialize data */ + sd->batched = 0; + sd->fifo_expire[SYNC][READ] = sync_read_expire; + sd->fifo_expire[SYNC][WRITE] = sync_write_expire; + sd->fifo_expire[ASYNC][READ] = async_read_expire; + sd->fifo_expire[ASYNC][WRITE] = async_write_expire; + sd->fifo_batch = fifo_batch; + + return sd; +} + +static void +sio_exit_queue(struct elevator_queue *e) +{ + struct sio_data *sd = e->elevator_data; + + BUG_ON(!list_empty(&sd->fifo_list[SYNC][READ])); + BUG_ON(!list_empty(&sd->fifo_list[SYNC][WRITE])); + BUG_ON(!list_empty(&sd->fifo_list[ASYNC][READ])); + BUG_ON(!list_empty(&sd->fifo_list[ASYNC][WRITE])); + + /* Free structure */ + kfree(sd); +} + +/* + * sysfs code + */ + +static ssize_t +sio_var_show(int var, char *page) +{ + return sprintf(page, "%d\n", var); +} + +static ssize_t +sio_var_store(int *var, const char *page, size_t count) +{ + char *p = (char *) page; + + *var = simple_strtol(p, &p, 10); + return count; +} + +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct sio_data *sd = e->elevator_data; \ + int __data = __VAR; \ + if (__CONV) \ + __data = jiffies_to_msecs(__data); \ + return sio_var_show(__data, (page)); \ +} +SHOW_FUNCTION(sio_sync_read_expire_show, sd->fifo_expire[SYNC][READ], 1); +SHOW_FUNCTION(sio_sync_write_expire_show, sd->fifo_expire[SYNC][WRITE], 1); +SHOW_FUNCTION(sio_async_read_expire_show, sd->fifo_expire[ASYNC][READ], 1); +SHOW_FUNCTION(sio_async_write_expire_show, sd->fifo_expire[ASYNC][WRITE], 1); +SHOW_FUNCTION(sio_fifo_batch_show, sd->fifo_batch, 0); +SHOW_FUNCTION(sio_writes_starved_show, sd->writes_starved, 0); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct sio_data *sd = e->elevator_data; \ + int __data; \ + int ret = sio_var_store(&__data, (page), count); \ + if (__data < (MIN)) \ + __data = (MIN); \ + else if (__data > (MAX)) \ + __data = (MAX); \ + if (__CONV) \ + *(__PTR) = msecs_to_jiffies(__data); \ + else \ + *(__PTR) = __data; \ + return ret; \ +} +STORE_FUNCTION(sio_sync_read_expire_store, &sd->fifo_expire[SYNC][READ], 0, INT_MAX, 1); +STORE_FUNCTION(sio_sync_write_expire_store, &sd->fifo_expire[SYNC][WRITE], 0, INT_MAX, 1); +STORE_FUNCTION(sio_async_read_expire_store, &sd->fifo_expire[ASYNC][READ], 0, INT_MAX, 1); +STORE_FUNCTION(sio_async_write_expire_store, &sd->fifo_expire[ASYNC][WRITE], 0, INT_MAX, 1); +STORE_FUNCTION(sio_fifo_batch_store, &sd->fifo_batch, 0, INT_MAX, 0); +STORE_FUNCTION(sio_writes_starved_store, &sd->writes_starved, 0, INT_MAX, 0); +#undef STORE_FUNCTION + +#define DD_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, sio_##name##_show, \ + sio_##name##_store) + +static struct elv_fs_entry sio_attrs[] = { + DD_ATTR(sync_read_expire), + DD_ATTR(sync_write_expire), + DD_ATTR(async_read_expire), + DD_ATTR(async_write_expire), + DD_ATTR(fifo_batch), + DD_ATTR(writes_starved), + __ATTR_NULL +}; + +static struct elevator_type iosched_sio = { + .ops = { + .elevator_merge_req_fn = sio_merged_requests, + .elevator_dispatch_fn = sio_dispatch_requests, + .elevator_add_req_fn = sio_add_request, +#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,38) + .elevator_queue_empty_fn = sio_queue_empty, +#endif + .elevator_former_req_fn = sio_former_request, + .elevator_latter_req_fn = sio_latter_request, + .elevator_init_fn = sio_init_queue, + .elevator_exit_fn = sio_exit_queue, + }, + + .elevator_attrs = sio_attrs, + .elevator_name = "sio", + .elevator_owner = THIS_MODULE, +}; + +static int __init sio_init(void) +{ + /* Register elevator */ + elv_register(&iosched_sio); + + return 0; +} + +static void __exit sio_exit(void) +{ + /* Unregister elevator */ + elv_unregister(&iosched_sio); +} + +#ifdef CONFIG_FAST_RESUME +beforeresume_initcall(sio_init); +#else +module_init(sio_init); +#endif +module_exit(sio_exit); + +MODULE_AUTHOR("Miguel Boton"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Simple IO scheduler"); +MODULE_VERSION("0.2"); diff --git a/block/sioplus-iosched.c b/block/sioplus-iosched.c new file mode 100644 index 0000000..6809cb8 --- /dev/null +++ b/block/sioplus-iosched.c @@ -0,0 +1,405 @@ +/* + * Simple IO scheduler plus + * Based on Noop, Deadline and V(R) IO schedulers. + * + * Copyright (C) 2012 Miguel Boton + * (C) 2013, 2014 Boy Petersen + * + * + * This algorithm does not do any kind of sorting, as it is aimed for + * aleatory access devices, but it does some basic merging. We try to + * keep minimum overhead to achieve low latency. + * + * Asynchronous and synchronous requests are not treated separately, but + * we relay on deadlines to ensure fairness. + * + * The plus version incorporates several fixes and logic improvements. + * + */ +#include +#include +#include +#include +#include +#include + +enum { ASYNC, SYNC }; + +/* Tunables */ +static const int sync_read_expire = (HZ / 4); /* max time before a sync read is submitted. */ +static const int sync_write_expire = (HZ / 4) * 5; /* max time before a sync write is submitted. */ + +static const int async_read_expire = (HZ / 2); /* ditto for async, these limits are SOFT! */ +static const int async_write_expire = (HZ * 2); /* ditto for async, these limits are SOFT! */ + +static const int writes_starved = 1; /* max times reads can starve a write */ +static const int fifo_batch = 3; /* # of sequential requests treated as one + by the above parameters. For throughput. */ + +/* Elevator data */ +struct sio_data { + /* Request queues */ + struct list_head fifo_list[2][2]; + + /* Attributes */ + unsigned int batched; + unsigned int starved; + + /* Settings */ + int fifo_expire[2][2]; + int fifo_batch; + int writes_starved; +}; + +static void +sio_merged_requests(struct request_queue *q, struct request *rq, + struct request *next) +{ + /* + * If next expires before rq, assign its expire time to rq + * and move into next position (next will be deleted) in fifo. + */ + if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) { + if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) { + list_move(&rq->queuelist, &next->queuelist); + rq_set_fifo_time(rq, rq_fifo_time(next)); + } + } + + /* Delete next request */ + rq_fifo_clear(next); +} + +static void +sio_add_request(struct request_queue *q, struct request *rq) +{ + struct sio_data *sd = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + /* + * Add request to the proper fifo list and set its + * expire time. + */ + rq_set_fifo_time(rq, jiffies + sd->fifo_expire[sync][data_dir]); + list_add_tail(&rq->queuelist, &sd->fifo_list[sync][data_dir]); +} + +static int +sio_queue_empty(struct request_queue *q) +{ + struct sio_data *sd = q->elevator->elevator_data; + + /* Check if fifo lists are empty */ + return list_empty(&sd->fifo_list[SYNC][READ]) && list_empty(&sd->fifo_list[SYNC][WRITE]) && + list_empty(&sd->fifo_list[ASYNC][READ]) && list_empty(&sd->fifo_list[ASYNC][WRITE]); +} + +static struct request * +sio_expired_request(struct sio_data *sd, int sync, int data_dir) +{ + struct list_head *list = &sd->fifo_list[sync][data_dir]; + struct request *rq; + + if (list_empty(list)) + return NULL; + + /* Retrieve request */ + rq = rq_entry_fifo(list->next); + + /* Request has expired */ + if (time_after_eq(jiffies, rq_fifo_time(rq))) + return rq; + + return NULL; +} + +static struct request * +sio_choose_expired_request(struct sio_data *sd) +{ + struct request *rq; + + /* Reset (non-expired-)batch-counter */ + sd->batched = 0; + + /* + * Check expired requests. + * Asynchronous requests have priority over synchronous. + * Write requests have priority over read. + */ + rq = sio_expired_request(sd, ASYNC, WRITE); + if (rq) + return rq; + rq = sio_expired_request(sd, ASYNC, READ); + if (rq) + return rq; + + rq = sio_expired_request(sd, SYNC, WRITE); + if (rq) + return rq; + rq = sio_expired_request(sd, SYNC, READ); + if (rq) + return rq; + + + return NULL; +} + +static struct request * +sio_choose_request(struct sio_data *sd, int data_dir) +{ + struct list_head *sync = sd->fifo_list[SYNC]; + struct list_head *async = sd->fifo_list[ASYNC]; + + /* Increase (non-expired-)batch-counter */ + sd->batched++; + + /* + * Retrieve request from available fifo list. + * Synchronous requests have priority over asynchronous. + * Read requests have priority over write. + */ + if (!list_empty(&sync[data_dir])) + return rq_entry_fifo(sync[data_dir].next); + if (!list_empty(&async[data_dir])) + return rq_entry_fifo(async[data_dir].next); + + if (!list_empty(&sync[!data_dir])) + return rq_entry_fifo(sync[!data_dir].next); + if (!list_empty(&async[!data_dir])) + return rq_entry_fifo(async[!data_dir].next); + + return NULL; +} + +static inline void +sio_dispatch_request(struct sio_data *sd, struct request *rq) +{ + + /* + * Remove the request from the fifo list + * and dispatch it. + */ + rq_fifo_clear(rq); + elv_dispatch_add_tail(rq->q, rq); + + if (rq_data_dir(rq)) { + sd->starved = 0; + } else { + if (!list_empty(&sd->fifo_list[SYNC][WRITE]) || + !list_empty(&sd->fifo_list[ASYNC][WRITE])) + sd->starved++; + } +} + +static int +sio_dispatch_requests(struct request_queue *q, int force) +{ + struct sio_data *sd = q->elevator->elevator_data; + struct request *rq = NULL; + int data_dir = READ; + + /* + * Retrieve any expired request after a batch of + * sequential requests. + */ + if (sd->batched >= sd->fifo_batch) + rq = sio_choose_expired_request(sd); + + /* Retrieve request */ + if (!rq) { + if (sd->starved >= sd->writes_starved) + data_dir = WRITE; + + rq = sio_choose_request(sd, data_dir); + if (!rq) + return 0; + } + + /* Dispatch request */ + sio_dispatch_request(sd, rq); + + return 1; +} + +static struct request * +sio_former_request(struct request_queue *q, struct request *rq) +{ + struct sio_data *sd = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + if (rq->queuelist.prev == &sd->fifo_list[sync][data_dir]) + return NULL; + + /* Return former request */ + return list_entry(rq->queuelist.prev, struct request, queuelist); +} + +static struct request * +sio_latter_request(struct request_queue *q, struct request *rq) +{ + struct sio_data *sd = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + if (rq->queuelist.next == &sd->fifo_list[sync][data_dir]) + return NULL; + + /* Return latter request */ + return list_entry(rq->queuelist.next, struct request, queuelist); +} + +static void * +sio_init_queue(struct request_queue *q) +{ + struct sio_data *sd; + + /* Allocate structure */ + sd = kmalloc_node(sizeof(*sd), GFP_KERNEL, q->node); + if (!sd) + return NULL; + + /* Initialize fifo lists */ + INIT_LIST_HEAD(&sd->fifo_list[SYNC][READ]); + INIT_LIST_HEAD(&sd->fifo_list[SYNC][WRITE]); + INIT_LIST_HEAD(&sd->fifo_list[ASYNC][READ]); + INIT_LIST_HEAD(&sd->fifo_list[ASYNC][WRITE]); + + /* Initialize data */ + sd->batched = 0; + sd->fifo_expire[SYNC][READ] = sync_read_expire; + sd->fifo_expire[SYNC][WRITE] = sync_write_expire; + sd->fifo_expire[ASYNC][READ] = async_read_expire; + sd->fifo_expire[ASYNC][WRITE] = async_write_expire; + sd->fifo_batch = fifo_batch; + sd->writes_starved = writes_starved; + + return sd; +} + +static void +sio_exit_queue(struct elevator_queue *e) +{ + struct sio_data *sd = e->elevator_data; + + BUG_ON(!list_empty(&sd->fifo_list[SYNC][READ])); + BUG_ON(!list_empty(&sd->fifo_list[SYNC][WRITE])); + BUG_ON(!list_empty(&sd->fifo_list[ASYNC][READ])); + BUG_ON(!list_empty(&sd->fifo_list[ASYNC][WRITE])); + + /* Free structure */ + kfree(sd); +} + +/* + * sysfs code + */ + +static ssize_t +sio_var_show(int var, char *page) +{ + return sprintf(page, "%d\n", var); +} + +static ssize_t +sio_var_store(int *var, const char *page, size_t count) +{ + char *p = (char *) page; + + *var = simple_strtol(p, &p, 10); + return count; +} + +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct sio_data *sd = e->elevator_data; \ + int __data = __VAR; \ + if (__CONV) \ + __data = jiffies_to_msecs(__data); \ + return sio_var_show(__data, (page)); \ +} +SHOW_FUNCTION(sio_sync_read_expire_show, sd->fifo_expire[SYNC][READ], 1); +SHOW_FUNCTION(sio_sync_write_expire_show, sd->fifo_expire[SYNC][WRITE], 1); +SHOW_FUNCTION(sio_async_read_expire_show, sd->fifo_expire[ASYNC][READ], 1); +SHOW_FUNCTION(sio_async_write_expire_show, sd->fifo_expire[ASYNC][WRITE], 1); +SHOW_FUNCTION(sio_fifo_batch_show, sd->fifo_batch, 0); +SHOW_FUNCTION(sio_writes_starved_show, sd->writes_starved, 0); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct sio_data *sd = e->elevator_data; \ + int __data; \ + int ret = sio_var_store(&__data, (page), count); \ + if (__data < (MIN)) \ + __data = (MIN); \ + else if (__data > (MAX)) \ + __data = (MAX); \ + if (__CONV) \ + *(__PTR) = msecs_to_jiffies(__data); \ + else \ + *(__PTR) = __data; \ + return ret; \ +} +STORE_FUNCTION(sio_sync_read_expire_store, &sd->fifo_expire[SYNC][READ], 0, INT_MAX, 1); +STORE_FUNCTION(sio_sync_write_expire_store, &sd->fifo_expire[SYNC][WRITE], 0, INT_MAX, 1); +STORE_FUNCTION(sio_async_read_expire_store, &sd->fifo_expire[ASYNC][READ], 0, INT_MAX, 1); +STORE_FUNCTION(sio_async_write_expire_store, &sd->fifo_expire[ASYNC][WRITE], 0, INT_MAX, 1); +STORE_FUNCTION(sio_fifo_batch_store, &sd->fifo_batch, 1, INT_MAX, 0); +STORE_FUNCTION(sio_writes_starved_store, &sd->writes_starved, 1, INT_MAX, 0); +#undef STORE_FUNCTION + +#define DD_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, sio_##name##_show, \ + sio_##name##_store) + +static struct elv_fs_entry sio_attrs[] = { + DD_ATTR(sync_read_expire), + DD_ATTR(sync_write_expire), + DD_ATTR(async_read_expire), + DD_ATTR(async_write_expire), + DD_ATTR(fifo_batch), + DD_ATTR(writes_starved), + __ATTR_NULL +}; + +static struct elevator_type iosched_sioplus = { + .ops = { + .elevator_merge_req_fn = sio_merged_requests, + .elevator_dispatch_fn = sio_dispatch_requests, + .elevator_add_req_fn = sio_add_request, + .elevator_queue_empty_fn = sio_queue_empty, + .elevator_former_req_fn = sio_former_request, + .elevator_latter_req_fn = sio_latter_request, + .elevator_init_fn = sio_init_queue, + .elevator_exit_fn = sio_exit_queue, + }, + + .elevator_attrs = sio_attrs, + .elevator_name = "sioplus", + .elevator_owner = THIS_MODULE, +}; + +static int __init sioplus_init(void) +{ + /* Register elevator */ + elv_register(&iosched_sioplus); + + return 0; +} + +static void __exit sioplus_exit(void) +{ + /* Unregister elevator */ + elv_unregister(&iosched_sioplus); +} + +module_init(sioplus_init); +module_exit(sioplus_exit); + +MODULE_AUTHOR("Miguel Boton"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Simple IO scheduler plus"); diff --git a/block/tripndroid-iosched.c b/block/tripndroid-iosched.c new file mode 100644 index 0000000..a4d0080 --- /dev/null +++ b/block/tripndroid-iosched.c @@ -0,0 +1,261 @@ +/* + * Copyright (c) 2013, TripNDroid Mobile Engineering + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + */ + +#include +#include +#include +#include +#include + +enum { ASYNC, SYNC }; + +static const int sync_read_expire = 1 * HZ; /* max time before a sync read is submitted. */ +static const int sync_write_expire = 1 * HZ; /* max time before a sync write is submitted. */ +static const int async_read_expire = 2 * HZ; /* ditto for async, these limits are SOFT! */ +static const int async_write_expire = 2 * HZ; /* ditto for async, these limits are SOFT! */ + +static const int writes_starved = 1; /* max times reads can starve a write */ +static const int fifo_batch = 1; /* # of sequential requests treated as one + by the above parameters. For throughput. */ + +struct tripndroid_data { + + struct list_head fifo_list[2][2]; + + unsigned int batched; + unsigned int starved; + + int fifo_expire[2][2]; + int fifo_batch; + int writes_starved; +}; + +static void tripndroid_merged_requests(struct request_queue *q, struct request *rq, + struct request *next) +{ + /* + * If next expires before rq, assign its expire time to rq + * and move into next position (next will be deleted) in fifo. + */ + if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) { + if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) { + list_move(&rq->queuelist, &next->queuelist); + rq_set_fifo_time(rq, rq_fifo_time(next)); + } + } + + rq_fifo_clear(next); +} + +static void tripndroid_add_request(struct request_queue *q, struct request *rq) +{ + struct tripndroid_data *td = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + rq_set_fifo_time(rq, jiffies + td->fifo_expire[sync][data_dir]); + list_add(&rq->queuelist, &td->fifo_list[sync][data_dir]); +} + +static struct request *tripndroid_expired_request(struct tripndroid_data *td, int sync, int data_dir) +{ + struct list_head *list = &td->fifo_list[sync][data_dir]; + struct request *rq; + + if (list_empty(list)) + return NULL; + + rq = rq_entry_fifo(list->next); + + if (time_after_eq(jiffies, rq_fifo_time(rq))) + return rq; + + return NULL; +} + +static struct request *tripndroid_choose_expired_request(struct tripndroid_data *td) +{ + struct request *rq; + + /* Asynchronous requests have priority over synchronous. + * Write requests have priority over read. */ + + rq = tripndroid_expired_request(td, ASYNC, WRITE); + if (rq) + return rq; + rq = tripndroid_expired_request(td, ASYNC, READ); + if (rq) + return rq; + + rq = tripndroid_expired_request(td, SYNC, WRITE); + if (rq) + return rq; + rq = tripndroid_expired_request(td, SYNC, READ); + if (rq) + return rq; + + return NULL; +} + +static struct request *tripndroid_choose_request(struct tripndroid_data *td, int data_dir) +{ + struct list_head *sync = td->fifo_list[SYNC]; + struct list_head *async = td->fifo_list[ASYNC]; + + if (!list_empty(&sync[data_dir])) + return rq_entry_fifo(sync[data_dir].next); + if (!list_empty(&sync[!data_dir])) + return rq_entry_fifo(sync[!data_dir].next); + + if (!list_empty(&async[data_dir])) + return rq_entry_fifo(async[data_dir].next); + if (!list_empty(&async[!data_dir])) + return rq_entry_fifo(async[!data_dir].next); + + return NULL; +} + +static inline void tripndroid_dispatch_request(struct tripndroid_data *td, struct request *rq) +{ + /* Dispatch the request */ + rq_fifo_clear(rq); + elv_dispatch_add_tail(rq->q, rq); + + td->batched++; + + if (rq_data_dir(rq)) + td->starved = 0; + else + td->starved++; +} + +static int tripndroid_dispatch_requests(struct request_queue *q, int force) +{ + struct tripndroid_data *td = q->elevator->elevator_data; + struct request *rq = NULL; + int data_dir = READ; + + if (td->batched > td->fifo_batch) { + td->batched = 0; + rq = tripndroid_choose_expired_request(td); + } + + if (!rq) { + if (td->starved > td->writes_starved) + data_dir = WRITE; + + rq = tripndroid_choose_request(td, data_dir); + if (!rq) + return 0; + } + + tripndroid_dispatch_request(td, rq); + + return 1; +} + +static struct request *tripndroid_former_request(struct request_queue *q, struct request *rq) +{ + struct tripndroid_data *td = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + if (rq->queuelist.prev == &td->fifo_list[sync][data_dir]) + return NULL; + + return list_entry(rq->queuelist.prev, struct request, queuelist); +} + +static struct request *tripndroid_latter_request(struct request_queue *q, struct request *rq) +{ + struct tripndroid_data *td = q->elevator->elevator_data; + const int sync = rq_is_sync(rq); + const int data_dir = rq_data_dir(rq); + + if (rq->queuelist.next == &td->fifo_list[sync][data_dir]) + return NULL; + + return list_entry(rq->queuelist.next, struct request, queuelist); +} + +static void *tripndroid_init_queue(struct request_queue *q) +{ + struct tripndroid_data *td; + + td = kmalloc_node(sizeof(*td), GFP_KERNEL, q->node); + if (!td) + return NULL; + + INIT_LIST_HEAD(&td->fifo_list[SYNC][READ]); + INIT_LIST_HEAD(&td->fifo_list[SYNC][WRITE]); + INIT_LIST_HEAD(&td->fifo_list[ASYNC][READ]); + INIT_LIST_HEAD(&td->fifo_list[ASYNC][WRITE]); + + td->batched = 0; + td->fifo_expire[SYNC][READ] = sync_read_expire; + td->fifo_expire[SYNC][WRITE] = sync_write_expire; + td->fifo_expire[ASYNC][READ] = async_read_expire; + td->fifo_expire[ASYNC][WRITE] = async_write_expire; + td->fifo_batch = fifo_batch; + + return td; +} + +static void tripndroid_exit_queue(struct elevator_queue *e) +{ + struct tripndroid_data *td = e->elevator_data; + + BUG_ON(!list_empty(&td->fifo_list[SYNC][READ])); + BUG_ON(!list_empty(&td->fifo_list[SYNC][WRITE])); + BUG_ON(!list_empty(&td->fifo_list[ASYNC][READ])); + BUG_ON(!list_empty(&td->fifo_list[ASYNC][WRITE])); + + kfree(td); +} + +static struct elevator_type iosched_tripndroid = { + .ops = { + .elevator_merge_req_fn = tripndroid_merged_requests, + .elevator_dispatch_fn = tripndroid_dispatch_requests, + .elevator_add_req_fn = tripndroid_add_request, + .elevator_former_req_fn = tripndroid_former_request, + .elevator_latter_req_fn = tripndroid_latter_request, + .elevator_init_fn = tripndroid_init_queue, + .elevator_exit_fn = tripndroid_exit_queue, + }, + .elevator_name = "tripndroid", + .elevator_owner = THIS_MODULE, +}; + +static int __init tripndroid_init(void) +{ + elv_register(&iosched_tripndroid); + return 0; +} + +static void __exit tripndroid_exit(void) +{ + elv_unregister(&iosched_tripndroid); +} + +module_init(tripndroid_init); +module_exit(tripndroid_exit); + +MODULE_AUTHOR("TripNRaVeR"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("TripNDroid IO Scheduler"); diff --git a/block/vr-iosched.c b/block/vr-iosched.c new file mode 100644 index 0000000..5d8954b --- /dev/null +++ b/block/vr-iosched.c @@ -0,0 +1,432 @@ +/* +* V(R) I/O Scheduler +* +* Copyright (C) 2007 Aaron Carroll +* +* +* The algorithm: +* +* The next request is decided based on its distance from the last +* request, with a multiplicative penalty of `rev_penalty' applied +* for reversing the head direction. A rev_penalty of 1 means SSTF +* behaviour. As this variable is increased, the algorithm approaches +* pure SCAN. Setting rev_penalty to 0 forces SCAN. +* +* Async and synch requests are not treated seperately. Instead we +* rely on deadlines to ensure fairness. +* +*/ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +enum vr_data_dir { + ASYNC, + SYNC, +}; + +enum vr_head_dir { + FORWARD, + BACKWARD, +}; + +static const int sync_expire = HZ / 2; /* max time before a sync is submitted. */ +static const int async_expire = 5 * HZ; /* ditto for async, these limits are SOFT! */ +static const int fifo_batch = 1; +static const int rev_penalty = 10; /* penalty for reversing head direction */ + +struct vr_data { +struct rb_root sort_list; +struct list_head fifo_list[2]; + +struct request *next_rq; +struct request *prev_rq; + +unsigned int nbatched; +sector_t last_sector; /* head position */ +int head_dir; + +/* tunables */ +int fifo_expire[2]; +int fifo_batch; +int rev_penalty; +}; + +static void vr_move_request(struct vr_data *, struct request *); + +static inline struct vr_data * +vr_get_data(struct request_queue *q) +{ + return q->elevator->elevator_data; +} + +static void +vr_add_rq_rb(struct vr_data *vd, struct request *rq) +{ + elv_rb_add(&vd->sort_list, rq); + + if (blk_rq_pos(rq) >= vd->last_sector) { + if (!vd->next_rq || blk_rq_pos(vd->next_rq) > blk_rq_pos(rq)) + vd->next_rq = rq; + } else { + if (!vd->prev_rq || blk_rq_pos(vd->prev_rq) < blk_rq_pos(rq)) + vd->prev_rq = rq; + } + + BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq); + BUG_ON(vd->next_rq && vd->prev_rq && blk_rq_pos(vd->next_rq) < blk_rq_pos(vd->prev_rq)); +} + +static void +vr_del_rq_rb(struct vr_data *vd, struct request *rq) +{ + /* + * We might be deleting our cached next request. + * If so, find its sucessor. + */ + + if (vd->next_rq == rq) + vd->next_rq = elv_rb_latter_request(NULL, rq); + else if (vd->prev_rq == rq) + vd->prev_rq = elv_rb_former_request(NULL, rq); + + BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq); + BUG_ON(vd->next_rq && vd->prev_rq && blk_rq_pos(vd->next_rq) < blk_rq_pos(vd->prev_rq)); + + elv_rb_del(&vd->sort_list, rq); +} + +/* + * add rq to rbtree and fifo + */ +static void +vr_add_request(struct request_queue *q, struct request *rq) +{ + struct vr_data *vd = vr_get_data(q); + const int dir = rq_is_sync(rq); + + vr_add_rq_rb(vd, rq); + + if (vd->fifo_expire[dir]) { + rq_set_fifo_time(rq, jiffies + vd->fifo_expire[dir]); + list_add_tail(&rq->queuelist, &vd->fifo_list[dir]); + } +} + +/* + * remove rq from rbtree and fifo. + */ +static void +vr_remove_request(struct request_queue *q, struct request *rq) +{ + struct vr_data *vd = vr_get_data(q); + + rq_fifo_clear(rq); + vr_del_rq_rb(vd, rq); +} + +static int +vr_merge(struct request_queue *q, struct request **rqp, struct bio *bio) +{ + sector_t sector = bio->bi_sector + bio_sectors(bio); + struct vr_data *vd = vr_get_data(q); + struct request *rq = elv_rb_find(&vd->sort_list, sector); + + if (rq && elv_rq_merge_ok(rq, bio)) { + *rqp = rq; + return ELEVATOR_FRONT_MERGE; + } + return ELEVATOR_NO_MERGE; +} + +static void +vr_merged_request(struct request_queue *q, struct request *req, int type) +{ + struct vr_data *vd = vr_get_data(q); + + /* + * if the merge was a front merge, we need to reposition request + */ + if (type == ELEVATOR_FRONT_MERGE) { + vr_del_rq_rb(vd, req); + vr_add_rq_rb(vd, req); + } +} + +static void +vr_merged_requests(struct request_queue *q, struct request *rq, +struct request *next) +{ + /* + * if next expires before rq, assign its expire time to rq + * and move into next position (next will be deleted) in fifo + */ + if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) { + if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) { + list_move(&rq->queuelist, &next->queuelist); + rq_set_fifo_time(rq, rq_fifo_time(next)); + } + } + + vr_remove_request(q, next); +} + +/* + * move an entry to dispatch queue + */ +static void +vr_move_request(struct vr_data *vd, struct request *rq) +{ + struct request_queue *q = rq->q; + + if (blk_rq_pos(rq) > vd->last_sector) + vd->head_dir = FORWARD; + else + vd->head_dir = BACKWARD; + + vd->last_sector = blk_rq_pos(rq); + vd->next_rq = elv_rb_latter_request(NULL, rq); + vd->prev_rq = elv_rb_former_request(NULL, rq); + + BUG_ON(vd->next_rq && vd->next_rq == vd->prev_rq); + + vr_remove_request(q, rq); + elv_dispatch_add_tail(q, rq); + vd->nbatched++; +} + +/* + * get the first expired request in direction ddir + */ +static struct request * +vr_expired_request(struct vr_data *vd, int ddir) +{ + struct request *rq; + + if (list_empty(&vd->fifo_list[ddir])) + return NULL; + + rq = rq_entry_fifo(vd->fifo_list[ddir].next); + if (time_after(jiffies, rq_fifo_time(rq))) + return rq; + + return NULL; +} + +/* + * Returns the oldest expired request + */ +static struct request * +vr_check_fifo(struct vr_data *vd) +{ + struct request *rq_sync = vr_expired_request(vd, SYNC); + struct request *rq_async = vr_expired_request(vd, ASYNC); + + if (rq_async && rq_sync) { + if (time_after(rq_fifo_time(rq_async), rq_fifo_time(rq_sync))) + return rq_sync; + } + else if (rq_sync) + return rq_sync; + + return rq_async; +} + +/* +* Return the request with the lowest penalty +*/ +static struct request * +vr_choose_request(struct vr_data *vd) +{ + int penalty = (vd->rev_penalty) ? : INT_MAX; + struct request *next = vd->next_rq; + struct request *prev = vd->prev_rq; + sector_t next_pen, prev_pen; + + BUG_ON(prev && prev == next); + + if (!prev) + return next; + else if (!next) + return prev; + +/* At this point both prev and next are defined and distinct */ + + next_pen = blk_rq_pos(next) - vd->last_sector; + prev_pen = vd->last_sector - blk_rq_pos(prev); + + if (vd->head_dir == FORWARD) + next_pen = do_div(next_pen, penalty); + else + prev_pen = do_div(prev_pen, penalty); + + if (next_pen <= prev_pen) + return next; + + return prev; +} + +static int +vr_dispatch_requests(struct request_queue *q, int force) +{ + struct vr_data *vd = vr_get_data(q); + struct request *rq = NULL; + +/* Check for and issue expired requests */ + if (vd->nbatched > vd->fifo_batch) { + vd->nbatched = 0; + rq = vr_check_fifo(vd); + } + + if (!rq) { + rq = vr_choose_request(vd); + if (!rq) + return 0; + } + + vr_move_request(vd, rq); + + return 1; +} + + +static void +vr_exit_queue(struct elevator_queue *e) +{ + struct vr_data *vd = e->elevator_data; + BUG_ON(!RB_EMPTY_ROOT(&vd->sort_list)); + kfree(vd); +} + +/* +* initialize elevator private data (vr_data). +*/ +static void *vr_init_queue(struct request_queue *q) +{ + struct vr_data *vd; + + vd = kmalloc_node(sizeof(*vd), GFP_KERNEL | __GFP_ZERO, q->node); + if (!vd) + return NULL; + + INIT_LIST_HEAD(&vd->fifo_list[SYNC]); + INIT_LIST_HEAD(&vd->fifo_list[ASYNC]); + vd->sort_list = RB_ROOT; + vd->fifo_expire[SYNC] = sync_expire; + vd->fifo_expire[ASYNC] = async_expire; + vd->fifo_batch = fifo_batch; + vd->rev_penalty = rev_penalty; + return vd; +} + +/* + * sysfs parts below + */ + +static ssize_t +vr_var_show(int var, char *page) +{ + return sprintf(page, "%d\n", var); +} + +static ssize_t +vr_var_store(int *var, const char *page, size_t count) +{ + *var = simple_strtol(page, NULL, 10); + return count; +} + +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ +struct vr_data *vd = e->elevator_data; \ +int __data = __VAR; \ +if (__CONV) \ +__data = jiffies_to_msecs(__data); \ +return vr_var_show(__data, (page)); \ +} +SHOW_FUNCTION(vr_sync_expire_show, vd->fifo_expire[SYNC], 1); +SHOW_FUNCTION(vr_async_expire_show, vd->fifo_expire[ASYNC], 1); +SHOW_FUNCTION(vr_fifo_batch_show, vd->fifo_batch, 0); +SHOW_FUNCTION(vr_rev_penalty_show, vd->rev_penalty, 0); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ +struct vr_data *vd = e->elevator_data; \ +int __data; \ +int ret = vr_var_store(&__data, (page), count); \ +if (__data < (MIN)) \ +__data = (MIN); \ +else if (__data > (MAX)) \ +__data = (MAX); \ +if (__CONV) \ +*(__PTR) = msecs_to_jiffies(__data); \ +else \ +*(__PTR) = __data; \ +return ret; \ +} +STORE_FUNCTION(vr_sync_expire_store, &vd->fifo_expire[SYNC], 0, INT_MAX, 1); +STORE_FUNCTION(vr_async_expire_store, &vd->fifo_expire[ASYNC], 0, INT_MAX, 1); +STORE_FUNCTION(vr_fifo_batch_store, &vd->fifo_batch, 0, INT_MAX, 0); +STORE_FUNCTION(vr_rev_penalty_store, &vd->rev_penalty, 0, INT_MAX, 0); +#undef STORE_FUNCTION + +#define DD_ATTR(name) \ +__ATTR(name, S_IRUGO|S_IWUSR, vr_##name##_show, \ +vr_##name##_store) + +static struct elv_fs_entry vr_attrs[] = { + DD_ATTR(sync_expire), + DD_ATTR(async_expire), + DD_ATTR(fifo_batch), + DD_ATTR(rev_penalty), + __ATTR_NULL +}; + +static struct elevator_type iosched_vr = { + .ops = { + .elevator_merge_fn = vr_merge, + .elevator_merged_fn = vr_merged_request, + .elevator_merge_req_fn = vr_merged_requests, + .elevator_dispatch_fn = vr_dispatch_requests, + .elevator_add_req_fn = vr_add_request, + .elevator_former_req_fn = elv_rb_former_request, + .elevator_latter_req_fn = elv_rb_latter_request, + .elevator_init_fn = vr_init_queue, + .elevator_exit_fn = vr_exit_queue, + }, + + .elevator_attrs = vr_attrs, + .elevator_name = "vr", + .elevator_owner = THIS_MODULE, +}; + +static int __init vr_init(void) +{ + elv_register(&iosched_vr); + + return 0; +} + +static void __exit vr_exit(void) +{ + elv_unregister(&iosched_vr); +} + +module_init(vr_init); +module_exit(vr_exit); + +MODULE_AUTHOR("Aaron Carroll"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("V(R) IO scheduler"); diff --git a/block/zen-iosched.c b/block/zen-iosched.c new file mode 100644 index 0000000..77145de --- /dev/null +++ b/block/zen-iosched.c @@ -0,0 +1,277 @@ +/* + * Zen IO scheduler + * Primarily based on Noop, deadline, and SIO IO schedulers. + * + * Copyright (C) 2012 Brandon Berhent + * + * FCFS, dispatches are back-inserted, deadlines ensure fairness. + * Should work best with devices where there is no travel delay. + */ +#include +#include +#include +#include +#include +#include + +enum zen_data_dir { ASYNC, SYNC }; + +static const int sync_expire = HZ / 4; /* max time before a sync is submitted. */ +static const int async_expire = 2 * HZ; /* ditto for async, these limits are SOFT! */ +static const int fifo_batch = 1; + +struct zen_data { + /* Runtime Data */ + /* Requests are only present on fifo_list */ + struct list_head fifo_list[2]; + + unsigned int batching; /* number of sequential requests made */ + + /* tunables */ + int fifo_expire[2]; + int fifo_batch; +}; + +static inline struct zen_data * +zen_get_data(struct request_queue *q) { + return q->elevator->elevator_data; +} + +static void zen_dispatch(struct zen_data *, struct request *); + +static void +zen_merged_requests(struct request_queue *q, struct request *rq, + struct request *next) +{ + /* + * if next expires before rq, assign its expire time to arq + * and move into next position (next will be deleted) in fifo + */ + if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist)) { + if (time_before(rq_fifo_time(next), rq_fifo_time(rq))) { + list_move(&rq->queuelist, &next->queuelist); + rq_set_fifo_time(rq, rq_fifo_time(next)); + } + } + + /* next request is gone */ + rq_fifo_clear(next); +} + +static void zen_add_request(struct request_queue *q, struct request *rq) +{ + struct zen_data *zdata = zen_get_data(q); + const int dir = rq_data_dir(rq); + + if (zdata->fifo_expire[dir]) { + rq_set_fifo_time(rq, jiffies + zdata->fifo_expire[dir]); + list_add_tail(&rq->queuelist, &zdata->fifo_list[dir]); + } +} + +static void zen_dispatch(struct zen_data *zdata, struct request *rq) +{ + /* Remove request from list and dispatch it */ + rq_fifo_clear(rq); + elv_dispatch_add_tail(rq->q, rq); + + /* Increment # of sequential requests */ + zdata->batching++; +} + +/* + * get the first expired request in direction ddir + */ +static struct request * +zen_expired_request(struct zen_data *zdata, int ddir) +{ + struct request *rq; + + if (list_empty(&zdata->fifo_list[ddir])) + return NULL; + + rq = rq_entry_fifo(zdata->fifo_list[ddir].next); + if (time_after(jiffies, rq_fifo_time(rq))) + return rq; + + return NULL; +} + +/* + * zen_check_fifo returns 0 if there are no expired requests on the fifo, + * otherwise it returns the next expired request + */ +static struct request * +zen_check_fifo(struct zen_data *zdata) +{ + struct request *rq_sync = zen_expired_request(zdata, SYNC); + struct request *rq_async = zen_expired_request(zdata, ASYNC); + + if (rq_async && rq_sync) { + if (time_after(rq_fifo_time(rq_async), rq_fifo_time(rq_sync))) + return rq_sync; + } else if (rq_sync) { + return rq_sync; + } else if (rq_async) { + return rq_async; + } + + return 0; +} + +static struct request * +zen_choose_request(struct zen_data *zdata) +{ + /* + * Retrieve request from available fifo list. + * Synchronous requests have priority over asynchronous. + */ + if (!list_empty(&zdata->fifo_list[SYNC])) + return rq_entry_fifo(zdata->fifo_list[SYNC].next); + if (!list_empty(&zdata->fifo_list[ASYNC])) + return rq_entry_fifo(zdata->fifo_list[ASYNC].next); + + return NULL; +} + +static int zen_dispatch_requests(struct request_queue *q, int force) +{ + struct zen_data *zdata = zen_get_data(q); + struct request *rq = NULL; + + /* Check for and issue expired requests */ + if (zdata->batching > zdata->fifo_batch) { + zdata->batching = 0; + rq = zen_check_fifo(zdata); + } + + if (!rq) { + rq = zen_choose_request(zdata); + if (!rq) + return 0; + } + + zen_dispatch(zdata, rq); + + return 1; +} + +static void *zen_init_queue(struct request_queue *q) +{ + struct zen_data *zdata; + + zdata = kmalloc_node(sizeof(*zdata), GFP_KERNEL, q->node); + if (!zdata) + return NULL; + INIT_LIST_HEAD(&zdata->fifo_list[SYNC]); + INIT_LIST_HEAD(&zdata->fifo_list[ASYNC]); + zdata->fifo_expire[SYNC] = sync_expire; + zdata->fifo_expire[ASYNC] = async_expire; + zdata->fifo_batch = fifo_batch; + return zdata; +} + +static void zen_exit_queue(struct elevator_queue *e) +{ + struct zen_data *zdata = e->elevator_data; + + BUG_ON(!list_empty(&zdata->fifo_list[SYNC])); + BUG_ON(!list_empty(&zdata->fifo_list[ASYNC])); + kfree(zdata); +} + +/* Sysfs */ +static ssize_t +zen_var_show(int var, char *page) +{ + return sprintf(page, "%d\n", var); +} + +static ssize_t +zen_var_store(int *var, const char *page, size_t count) +{ + *var = simple_strtol(page, NULL, 10); + return count; +} + +#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, char *page) \ +{ \ + struct zen_data *zdata = e->elevator_data; \ + int __data = __VAR; \ + if (__CONV) \ + __data = jiffies_to_msecs(__data); \ + return zen_var_show(__data, (page)); \ +} +SHOW_FUNCTION(zen_sync_expire_show, zdata->fifo_expire[SYNC], 1); +SHOW_FUNCTION(zen_async_expire_show, zdata->fifo_expire[ASYNC], 1); +SHOW_FUNCTION(zen_fifo_batch_show, zdata->fifo_batch, 0); +#undef SHOW_FUNCTION + +#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ +static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \ +{ \ + struct zen_data *zdata = e->elevator_data; \ + int __data; \ + int ret = zen_var_store(&__data, (page), count); \ + if (__data < (MIN)) \ + __data = (MIN); \ + else if (__data > (MAX)) \ + __data = (MAX); \ + if (__CONV) \ + *(__PTR) = msecs_to_jiffies(__data); \ + else \ + *(__PTR) = __data; \ + return ret; \ +} +STORE_FUNCTION(zen_sync_expire_store, &zdata->fifo_expire[SYNC], 0, INT_MAX, 1); +STORE_FUNCTION(zen_async_expire_store, &zdata->fifo_expire[ASYNC], 0, INT_MAX, 1); +STORE_FUNCTION(zen_fifo_batch_store, &zdata->fifo_batch, 0, INT_MAX, 0); +#undef STORE_FUNCTION + +#define DD_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, zen_##name##_show, \ + zen_##name##_store) + +static struct elv_fs_entry zen_attrs[] = { + DD_ATTR(sync_expire), + DD_ATTR(async_expire), + DD_ATTR(fifo_batch), + __ATTR_NULL +}; + +static struct elevator_type iosched_zen = { + .ops = { + .elevator_merge_req_fn = zen_merged_requests, + .elevator_dispatch_fn = zen_dispatch_requests, + .elevator_add_req_fn = zen_add_request, + .elevator_former_req_fn = elv_rb_former_request, + .elevator_latter_req_fn = elv_rb_latter_request, + .elevator_init_fn = zen_init_queue, + .elevator_exit_fn = zen_exit_queue, + }, + .elevator_attrs = zen_attrs, + .elevator_name = "zen", + .elevator_owner = THIS_MODULE, +}; + +static int __init zen_init(void) +{ + elv_register(&iosched_zen); + + return 0; +} + +static void __exit zen_exit(void) +{ + elv_unregister(&iosched_zen); +} + +module_init(zen_init); +module_exit(zen_exit); + + +MODULE_AUTHOR("Brandon Berhent"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Zen IO scheduler"); +MODULE_VERSION("1.0"); diff --git a/drivers/md/dm-builtin.c b/drivers/md/dm-builtin.c new file mode 100644 index 0000000..797daec --- /dev/null +++ b/drivers/md/dm-builtin.c @@ -0,0 +1,50 @@ +#include "dm.h" + +#include + +/* + * The kobject release method must not be placed in the module itself, + * otherwise we are subject to module unload races. + * + * The release method is called when the last reference to the kobject is + * dropped. It may be called by any other kernel code that drops the last + * reference. + * + * The release method suffers from module unload race. We may prevent the + * module from being unloaded at the start of the release method (using + * increased module reference count or synchronizing against the release + * method), however there is no way to prevent the module from being + * unloaded at the end of the release method. + * + * If this code were placed in the dm module, the following race may + * happen: + * 1. Some other process takes a reference to dm kobject + * 2. The user issues ioctl function to unload the dm device + * 3. dm_sysfs_exit calls kobject_put, however the object is not released + * because of the other reference taken at step 1 + * 4. dm_sysfs_exit waits on the completion + * 5. The other process that took the reference in step 1 drops it, + * dm_kobject_release is called from this process + * 6. dm_kobject_release calls complete() + * 7. a reschedule happens before dm_kobject_release returns + * 8. dm_sysfs_exit continues, the dm device is unloaded, module reference + * count is decremented + * 9. The user unloads the dm module + * 10. The other process that was rescheduled in step 7 continues to run, + * it is now executing code in unloaded module, so it crashes + * + * Note that if the process that takes the foreign reference to dm kobject + * has a low priority and the system is sufficiently loaded with + * higher-priority processes that prevent the low-priority process from + * being scheduled long enough, this bug may really happen. + * + * In order to fix this module unload race, we place the release method + * into a helper code that is compiled directly into the kernel. + */ + +void dm_kobject_release(struct kobject *kobj) +{ + complete(dm_get_completion_from_kobject(kobj)); +} + +EXPORT_SYMBOL(dm_kobject_release);