From ee63cfa7fc197b63669623721b8009cce5b0659b Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 24 Aug 2016 15:52:48 -0600 Subject: block: add kblockd_schedule_work_on() Add a helper to schedule a regular struct work on a particular CPU. Signed-off-by: Jens Axboe --- block/blk-core.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'block') diff --git a/block/blk-core.c b/block/blk-core.c index 36c7ac328d8c..2d08597533a4 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -3097,6 +3097,12 @@ int kblockd_schedule_work(struct work_struct *work) } EXPORT_SYMBOL(kblockd_schedule_work); +int kblockd_schedule_work_on(int cpu, struct work_struct *work) +{ + return queue_work_on(cpu, kblockd_workqueue, work); +} +EXPORT_SYMBOL(kblockd_schedule_work_on); + int kblockd_schedule_delayed_work(struct delayed_work *dwork, unsigned long delay) { -- cgit v1.2.3 From 27489a3c827b7eebba26eda0320bb0f100bef167 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 24 Aug 2016 15:54:25 -0600 Subject: blk-mq: turn hctx->run_work into a regular work struct We don't need the larger delayed work struct, since we always run it immediately. Signed-off-by: Jens Axboe --- block/blk-core.c | 2 +- block/blk-mq.c | 9 ++++----- include/linux/blk-mq.h | 2 +- 3 files changed, 6 insertions(+), 7 deletions(-) (limited to 'block') diff --git a/block/blk-core.c b/block/blk-core.c index 2d08597533a4..34ff8088eebe 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -288,7 +288,7 @@ void blk_sync_queue(struct request_queue *q) int i; queue_for_each_hw_ctx(q, hctx, i) { - cancel_delayed_work_sync(&hctx->run_work); + cancel_work_sync(&hctx->run_work); cancel_delayed_work_sync(&hctx->delay_work); } } else { diff --git a/block/blk-mq.c b/block/blk-mq.c index 13f5a6c1de76..b68fdcbe58f6 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -936,8 +936,7 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async) put_cpu(); } - kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx), - &hctx->run_work, 0); + kblockd_schedule_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work); } void blk_mq_run_hw_queues(struct request_queue *q, bool async) @@ -958,7 +957,7 @@ EXPORT_SYMBOL(blk_mq_run_hw_queues); void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx) { - cancel_delayed_work(&hctx->run_work); + cancel_work(&hctx->run_work); cancel_delayed_work(&hctx->delay_work); set_bit(BLK_MQ_S_STOPPED, &hctx->state); } @@ -1011,7 +1010,7 @@ static void blk_mq_run_work_fn(struct work_struct *work) { struct blk_mq_hw_ctx *hctx; - hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work); + hctx = container_of(work, struct blk_mq_hw_ctx, run_work); __blk_mq_run_hw_queue(hctx); } @@ -1722,7 +1721,7 @@ static int blk_mq_init_hctx(struct request_queue *q, if (node == NUMA_NO_NODE) node = hctx->numa_node = set->numa_node; - INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn); + INIT_WORK(&hctx->run_work, blk_mq_run_work_fn); INIT_DELAYED_WORK(&hctx->delay_work, blk_mq_delay_work_fn); spin_lock_init(&hctx->lock); INIT_LIST_HEAD(&hctx->dispatch); diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index e43bbffb5b7a..d579252e6463 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -25,7 +25,7 @@ struct blk_mq_hw_ctx { } ____cacheline_aligned_in_smp; unsigned long state; /* BLK_MQ_S_* flags */ - struct delayed_work run_work; + struct work_struct run_work; struct delayed_work delay_work; cpumask_var_t cpumask; int next_cpu; -- cgit v1.2.3 From 88c7b2b75132c3ff8180b71e4f06cf043a00eac8 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 25 Aug 2016 08:07:30 -0600 Subject: blk-mq: prefetch request in blk_mq_tag_to_rq() When drivers or the core calls this function, they usually dereference the request shortly there after. Prefetch the first cache line. Profiling IO workloads shows that this is the most common cache miss on the block side of things. Signed-off-by: Jens Axboe --- block/blk-mq.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'block') diff --git a/block/blk-mq.c b/block/blk-mq.c index b68fdcbe58f6..eea0d230faa1 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -22,6 +22,7 @@ #include #include #include +#include #include @@ -588,8 +589,10 @@ EXPORT_SYMBOL(blk_mq_abort_requeue_list); struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag) { - if (tag < tags->nr_tags) + if (tag < tags->nr_tags) { + prefetch(tags->rqs[tag]); return tags->rqs[tag]; + } return NULL; } -- cgit v1.2.3 From 6e219353afa1f67f453141f7462b01708ebf5574 Mon Sep 17 00:00:00 2001 From: Stephen Bates Date: Tue, 13 Sep 2016 12:23:15 -0600 Subject: block: add poll_considered statistic In order to help determine the effectiveness of polling in a running system it is usful to determine the ratio of how often the poll function is called vs how often the completion is checked. For this reason we add a poll_considered variable and add it to the sysfs entry for io_poll. Signed-off-by: Stephen Bates Acked-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-core.c | 8 ++++++-- block/blk-mq-sysfs.c | 4 +++- include/linux/blk-mq.h | 1 + 3 files changed, 10 insertions(+), 3 deletions(-) (limited to 'block') diff --git a/block/blk-core.c b/block/blk-core.c index 34ff8088eebe..14d7c0740dc0 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -3307,19 +3307,23 @@ bool blk_poll(struct request_queue *q, blk_qc_t cookie) { struct blk_plug *plug; long state; + unsigned int queue_num; + struct blk_mq_hw_ctx *hctx; if (!q->mq_ops || !q->mq_ops->poll || !blk_qc_t_valid(cookie) || !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) return false; + queue_num = blk_qc_t_to_queue_num(cookie); + hctx = q->queue_hw_ctx[queue_num]; + hctx->poll_considered++; + plug = current->plug; if (plug) blk_flush_plug_list(plug, false); state = current->state; while (!need_resched()) { - unsigned int queue_num = blk_qc_t_to_queue_num(cookie); - struct blk_mq_hw_ctx *hctx = q->queue_hw_ctx[queue_num]; int ret; hctx->poll_invoked++; diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index fe822aa5b8e4..ea8c3f58afbd 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -176,7 +176,9 @@ static ssize_t blk_mq_sysfs_rq_list_show(struct blk_mq_ctx *ctx, char *page) static ssize_t blk_mq_hw_sysfs_poll_show(struct blk_mq_hw_ctx *hctx, char *page) { - return sprintf(page, "invoked=%lu, success=%lu\n", hctx->poll_invoked, hctx->poll_success); + return sprintf(page, "considered=%lu, invoked=%lu, success=%lu\n", + hctx->poll_considered, hctx->poll_invoked, + hctx->poll_success); } static ssize_t blk_mq_hw_sysfs_queued_show(struct blk_mq_hw_ctx *hctx, diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index e1544f0f8c21..7710f795d7c2 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -61,6 +61,7 @@ struct blk_mq_hw_ctx { struct blk_mq_cpu_notifier cpu_notifier; struct kobject kobj; + unsigned long poll_considered; unsigned long poll_invoked; unsigned long poll_success; }; -- cgit v1.2.3 From d21ea4bc0f6afbc852f1436c7c691c7b6fed0eb8 Mon Sep 17 00:00:00 2001 From: Stephen Bates Date: Tue, 13 Sep 2016 12:23:16 -0600 Subject: block: enable zeroing of io_poll statistics Allow the io_poll statistics to be zeroed to make for easier logging of polling event. Signed-off-by: Stephen Bates Acked-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-mq-sysfs.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'block') diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index ea8c3f58afbd..ac5160eb6862 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -181,6 +181,14 @@ static ssize_t blk_mq_hw_sysfs_poll_show(struct blk_mq_hw_ctx *hctx, char *page) hctx->poll_success); } +static ssize_t blk_mq_hw_sysfs_poll_store(struct blk_mq_hw_ctx *hctx, + const char *page, size_t size) +{ + hctx->poll_considered = hctx->poll_invoked = hctx->poll_success = 0; + + return size; +} + static ssize_t blk_mq_hw_sysfs_queued_show(struct blk_mq_hw_ctx *hctx, char *page) { @@ -303,8 +311,9 @@ static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_cpus = { .show = blk_mq_hw_sysfs_cpus_show, }; static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_poll = { - .attr = {.name = "io_poll", .mode = S_IRUGO }, + .attr = {.name = "io_poll", .mode = S_IWUSR | S_IRUGO }, .show = blk_mq_hw_sysfs_poll_show, + .store = blk_mq_hw_sysfs_poll_store, }; static struct attribute *default_hw_ctx_attrs[] = { -- cgit v1.2.3 From a441b0d093b3690b7cc2cb30998358904d051db4 Mon Sep 17 00:00:00 2001 From: Linus Walleij Date: Wed, 14 Sep 2016 14:32:52 +0200 Subject: block: remove remnant refs to hardsect commit e1defc4ff0cf57aca6c5e3ff99fa503f5943c1f1 "block: Do away with the notion of hardsect_size" removed the notion of "hardware sector size" from the kernel in favor of logical block size, but references remain in comments and documentation. Update the remaining sites mentioning hardsect. Signed-off-by: Linus Walleij Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- Documentation/block/biodoc.txt | 4 ++-- block/bio.c | 2 +- fs/befs/linuxvfs.c | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-) (limited to 'block') diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt index bcdb2b4c1f12..918e1e0d0e78 100644 --- a/Documentation/block/biodoc.txt +++ b/Documentation/block/biodoc.txt @@ -115,7 +115,7 @@ i. Per-queue limits/values exported to the generic layer by the driver Various parameters that the generic i/o scheduler logic uses are set at a per-queue level (e.g maximum request size, maximum number of segments in -a scatter-gather list, hardsect size) +a scatter-gather list, logical block size) Some parameters that were earlier available as global arrays indexed by major/minor are now directly associated with the queue. Some of these may @@ -156,7 +156,7 @@ Some new queue property settings: blk_queue_max_segment_size(q, max_seg_size) Maximum size of a clustered segment, 64kB default. - blk_queue_hardsect_size(q, hardsect_size) + blk_queue_logical_block_size(q, logical_block_size) Lowest possible sector size that the hardware can operate on, 512 bytes default. diff --git a/block/bio.c b/block/bio.c index aa7354088008..a6d279e1ea9e 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1274,7 +1274,7 @@ struct bio *bio_map_user_iov(struct request_queue *q, nr_pages += end - start; /* - * buffer must be aligned to at least hardsector size for now + * buffer must be aligned to at least logical block size for now */ if (uaddr & queue_dma_alignment(q)) return ERR_PTR(-EINVAL); diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c index 7da05b159ade..bfe9f9994935 100644 --- a/fs/befs/linuxvfs.c +++ b/fs/befs/linuxvfs.c @@ -789,7 +789,7 @@ befs_fill_super(struct super_block *sb, void *data, int silent) * Will be set to real fs blocksize later. * * Linux 2.4.10 and later refuse to read blocks smaller than - * the hardsect size for the device. But we also need to read at + * the logical block size for the device. But we also need to read at * least 1k to get the second 512 bytes of the volume. * -WD 10-26-01 */ -- cgit v1.2.3 From 2849450ad39d2e699fda2d5c6f41e05d87fd7004 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 14 Sep 2016 13:28:30 -0400 Subject: blk-mq: introduce blk_mq_delay_kick_requeue_list() blk_mq_delay_kick_requeue_list() provides the ability to kick the q->requeue_list after a specified time. To do this the request_queue's 'requeue_work' member was changed to a delayed_work. blk_mq_delay_kick_requeue_list() allows DM to defer processing requeued requests while it doesn't make sense to immediately requeue them (e.g. when all paths in a DM multipath have failed). Signed-off-by: Mike Snitzer Signed-off-by: Jens Axboe --- block/blk-mq.c | 16 ++++++++++++---- include/linux/blk-mq.h | 1 + include/linux/blkdev.h | 2 +- 3 files changed, 14 insertions(+), 5 deletions(-) (limited to 'block') diff --git a/block/blk-mq.c b/block/blk-mq.c index eea0d230faa1..7ddc7969fba4 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -502,7 +502,7 @@ EXPORT_SYMBOL(blk_mq_requeue_request); static void blk_mq_requeue_work(struct work_struct *work) { struct request_queue *q = - container_of(work, struct request_queue, requeue_work); + container_of(work, struct request_queue, requeue_work.work); LIST_HEAD(rq_list); struct request *rq, *next; unsigned long flags; @@ -557,16 +557,24 @@ EXPORT_SYMBOL(blk_mq_add_to_requeue_list); void blk_mq_cancel_requeue_work(struct request_queue *q) { - cancel_work_sync(&q->requeue_work); + cancel_delayed_work_sync(&q->requeue_work); } EXPORT_SYMBOL_GPL(blk_mq_cancel_requeue_work); void blk_mq_kick_requeue_list(struct request_queue *q) { - kblockd_schedule_work(&q->requeue_work); + kblockd_schedule_delayed_work(&q->requeue_work, 0); } EXPORT_SYMBOL(blk_mq_kick_requeue_list); +void blk_mq_delay_kick_requeue_list(struct request_queue *q, + unsigned long msecs) +{ + kblockd_schedule_delayed_work(&q->requeue_work, + msecs_to_jiffies(msecs)); +} +EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list); + void blk_mq_abort_requeue_list(struct request_queue *q) { unsigned long flags; @@ -2084,7 +2092,7 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, q->sg_reserved_size = INT_MAX; - INIT_WORK(&q->requeue_work, blk_mq_requeue_work); + INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work); INIT_LIST_HEAD(&q->requeue_list); spin_lock_init(&q->requeue_lock); diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index ff14f68067aa..60ef14cbcd2d 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -233,6 +233,7 @@ void blk_mq_requeue_request(struct request *rq); void blk_mq_add_to_requeue_list(struct request *rq, bool at_head); void blk_mq_cancel_requeue_work(struct request_queue *q); void blk_mq_kick_requeue_list(struct request_queue *q); +void blk_mq_delay_kick_requeue_list(struct request_queue *q, unsigned long msecs); void blk_mq_abort_requeue_list(struct request_queue *q); void blk_mq_complete_request(struct request *rq, int error); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 69aae720f4ef..c47c358ba052 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -449,7 +449,7 @@ struct request_queue { struct list_head requeue_list; spinlock_t requeue_lock; - struct work_struct requeue_work; + struct delayed_work requeue_work; struct mutex sysfs_lock; -- cgit v1.2.3 From 703fd1c0f177219e3a84e6c095c31dc566514d81 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 16 Sep 2016 13:59:14 -0600 Subject: blk-mq: account higher order dispatch We currently account a '0' dispatch, and anything above that still falls below the range set by BLK_MQ_MAX_DISPATCH_ORDER. If we dispatch more, we don't account it. Change the last bucket to be inclusive of anything above the range we track, and have the sysfs file reflect that by including a '+' in the output: $ cat /sys/block/nvme0n1/mq/0/dispatched 0 1006 1 20229 2 1 4 0 8 0 16 0 32+ 0 Signed-off-by: Jens Axboe Reviewed-by: Omar Sandoval --- block/blk-mq-sysfs.c | 8 +++++--- block/blk-mq.c | 13 +++++++++---- 2 files changed, 14 insertions(+), 7 deletions(-) (limited to 'block') diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index ac5160eb6862..3c385b196bc7 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -208,12 +208,14 @@ static ssize_t blk_mq_hw_sysfs_dispatched_show(struct blk_mq_hw_ctx *hctx, page += sprintf(page, "%8u\t%lu\n", 0U, hctx->dispatched[0]); - for (i = 1; i < BLK_MQ_MAX_DISPATCH_ORDER; i++) { - unsigned long d = 1U << (i - 1); + for (i = 1; i < BLK_MQ_MAX_DISPATCH_ORDER - 1; i++) { + unsigned int d = 1U << (i - 1); - page += sprintf(page, "%8lu\t%lu\n", d, hctx->dispatched[i]); + page += sprintf(page, "%8u\t%lu\n", d, hctx->dispatched[i]); } + page += sprintf(page, "%8u+\t%lu\n", 1U << (i - 1), + hctx->dispatched[i]); return page - start_page; } diff --git a/block/blk-mq.c b/block/blk-mq.c index 7ddc7969fba4..0cb93625d812 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -789,6 +789,14 @@ static void flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list) } } +static inline unsigned int queued_to_index(unsigned int queued) +{ + if (!queued) + return 0; + + return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1); +} + /* * Run this hardware queue, pulling any software queues mapped to it in. * Note that this function currently has various problems around ordering @@ -877,10 +885,7 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) dptr = &driver_list; } - if (!queued) - hctx->dispatched[0]++; - else if (queued < (1 << (BLK_MQ_MAX_DISPATCH_ORDER - 1))) - hctx->dispatched[ilog2(queued) + 1]++; + hctx->dispatched[queued_to_index(queued)]++; /* * Any items that need requeuing? Stuff them into hctx->dispatch, -- cgit v1.2.3 From 88459642cba452630326b9cab1c651e09577d4e4 Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Sat, 17 Sep 2016 08:38:44 -0600 Subject: blk-mq: abstract tag allocation out into sbitmap library This is a generally useful data structure, so make it available to anyone else who might want to use it. It's also a nice cleanup separating the allocation logic from the rest of the tag handling logic. The code is behind a new Kconfig option, CONFIG_SBITMAP, which is only selected by CONFIG_BLOCK for now. This should be a complete noop functionality-wise. Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe --- MAINTAINERS | 1 + block/Kconfig | 1 + block/blk-mq-tag.c | 463 ++++++++++++------------------------------------ block/blk-mq-tag.h | 37 ++-- block/blk-mq.c | 112 ++++-------- block/blk-mq.h | 9 - include/linux/blk-mq.h | 9 +- include/linux/sbitmap.h | 327 ++++++++++++++++++++++++++++++++++ lib/Kconfig | 3 + lib/Makefile | 2 + lib/sbitmap.c | 301 +++++++++++++++++++++++++++++++ 11 files changed, 789 insertions(+), 476 deletions(-) create mode 100644 include/linux/sbitmap.h create mode 100644 lib/sbitmap.c (limited to 'block') diff --git a/MAINTAINERS b/MAINTAINERS index 71aa5daeae8f..157b1ca3e19d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2451,6 +2451,7 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git S: Maintained F: block/ F: kernel/trace/blktrace.c +F: lib/sbitmap.c BLOCK2MTD DRIVER M: Joern Engel diff --git a/block/Kconfig b/block/Kconfig index 161491d0a879..5136ad4bb6d5 100644 --- a/block/Kconfig +++ b/block/Kconfig @@ -4,6 +4,7 @@ menuconfig BLOCK bool "Enable the block layer" if EXPERT default y + select SBITMAP help Provide block layer support for the kernel. diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 729bac3a673b..2cbdecd594e9 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -1,12 +1,7 @@ /* - * Fast and scalable bitmap tagging variant. Uses sparser bitmaps spread - * over multiple cachelines to avoid ping-pong between multiple submitters - * or submitter and completer. Uses rolling wakeups to avoid falling of - * the scaling cliff when we run out of tags and have to start putting - * submitters to sleep. - * - * Uses active queue tracking to support fairer distribution of tags - * between multiple submitters when a shared tag map is used. + * Tag allocation using scalable bitmaps. Uses active queue tracking to support + * fairer distribution of tags between multiple submitters when a shared tag map + * is used. * * Copyright (C) 2013-2014 Jens Axboe */ @@ -19,40 +14,12 @@ #include "blk-mq.h" #include "blk-mq-tag.h" -static bool bt_has_free_tags(struct blk_mq_bitmap_tags *bt) -{ - int i; - - for (i = 0; i < bt->map_nr; i++) { - struct blk_align_bitmap *bm = &bt->map[i]; - int ret; - - ret = find_first_zero_bit(&bm->word, bm->depth); - if (ret < bm->depth) - return true; - } - - return false; -} - bool blk_mq_has_free_tags(struct blk_mq_tags *tags) { if (!tags) return true; - return bt_has_free_tags(&tags->bitmap_tags); -} - -static inline int bt_index_inc(int index) -{ - return (index + 1) & (BT_WAIT_QUEUES - 1); -} - -static inline void bt_index_atomic_inc(atomic_t *index) -{ - int old = atomic_read(index); - int new = bt_index_inc(old); - atomic_cmpxchg(index, old, new); + return sbitmap_any_bit_clear(&tags->bitmap_tags.sb); } /* @@ -72,29 +39,9 @@ bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx) */ void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve) { - struct blk_mq_bitmap_tags *bt; - int i, wake_index; - - /* - * Make sure all changes prior to this are visible from other CPUs. - */ - smp_mb(); - bt = &tags->bitmap_tags; - wake_index = atomic_read(&bt->wake_index); - for (i = 0; i < BT_WAIT_QUEUES; i++) { - struct bt_wait_state *bs = &bt->bs[wake_index]; - - if (waitqueue_active(&bs->wait)) - wake_up(&bs->wait); - - wake_index = bt_index_inc(wake_index); - } - - if (include_reserve) { - bt = &tags->breserved_tags; - if (waitqueue_active(&bt->bs[0].wait)) - wake_up(&bt->bs[0].wait); - } + sbitmap_queue_wake_all(&tags->bitmap_tags); + if (include_reserve) + sbitmap_queue_wake_all(&tags->breserved_tags); } /* @@ -118,7 +65,7 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx) * and attempt to provide a fair share of the tag depth for each of them. */ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, - struct blk_mq_bitmap_tags *bt) + struct sbitmap_queue *bt) { unsigned int depth, users; @@ -130,7 +77,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, /* * Don't try dividing an ant */ - if (bt->depth == 1) + if (bt->sb.depth == 1) return true; users = atomic_read(&hctx->tags->active_queues); @@ -140,127 +87,42 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, /* * Allow at least some tags */ - depth = max((bt->depth + users - 1) / users, 4U); + depth = max((bt->sb.depth + users - 1) / users, 4U); return atomic_read(&hctx->nr_active) < depth; } -static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag, - bool nowrap) -{ - int tag, org_last_tag = last_tag; - - while (1) { - tag = find_next_zero_bit(&bm->word, bm->depth, last_tag); - if (unlikely(tag >= bm->depth)) { - /* - * We started with an offset, and we didn't reset the - * offset to 0 in a failure case, so start from 0 to - * exhaust the map. - */ - if (org_last_tag && last_tag && !nowrap) { - last_tag = org_last_tag = 0; - continue; - } - return -1; - } - - if (!test_and_set_bit(tag, &bm->word)) - break; - - last_tag = tag + 1; - if (last_tag >= bm->depth - 1) - last_tag = 0; - } - - return tag; -} - #define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR) -/* - * Straight forward bitmap tag implementation, where each bit is a tag - * (cleared == free, and set == busy). The small twist is using per-cpu - * last_tag caches, which blk-mq stores in the blk_mq_ctx software queue - * contexts. This enables us to drastically limit the space searched, - * without dirtying an extra shared cacheline like we would if we stored - * the cache value inside the shared blk_mq_bitmap_tags structure. On top - * of that, each word of tags is in a separate cacheline. This means that - * multiple users will tend to stick to different cachelines, at least - * until the map is exhausted. - */ -static int __bt_get(struct blk_mq_hw_ctx *hctx, struct blk_mq_bitmap_tags *bt, +static int __bt_get(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt, unsigned int *tag_cache, struct blk_mq_tags *tags) { - unsigned int last_tag, org_last_tag; - int index, i, tag; + unsigned int last_tag; + int tag; if (!hctx_may_queue(hctx, bt)) return -1; - last_tag = org_last_tag = *tag_cache; - index = TAG_TO_INDEX(bt, last_tag); + last_tag = *tag_cache; + tag = sbitmap_get(&bt->sb, last_tag, BT_ALLOC_RR(tags)); - for (i = 0; i < bt->map_nr; i++) { - tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag), - BT_ALLOC_RR(tags)); - if (tag != -1) { - tag += (index << bt->bits_per_word); - goto done; - } - - /* - * Jump to next index, and reset the last tag to be the - * first tag of that index - */ - index++; - last_tag = (index << bt->bits_per_word); - - if (index >= bt->map_nr) { - index = 0; - last_tag = 0; - } - } - - *tag_cache = 0; - return -1; - - /* - * Only update the cache from the allocation path, if we ended - * up using the specific cached tag. - */ -done: - if (tag == org_last_tag || unlikely(BT_ALLOC_RR(tags))) { + if (tag == -1) { + *tag_cache = 0; + } else if (tag == last_tag || unlikely(BT_ALLOC_RR(tags))) { last_tag = tag + 1; - if (last_tag >= bt->depth - 1) + if (last_tag >= bt->sb.depth - 1) last_tag = 0; - *tag_cache = last_tag; } return tag; } -static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt, - struct blk_mq_hw_ctx *hctx) -{ - struct bt_wait_state *bs; - int wait_index; - - if (!hctx) - return &bt->bs[0]; - - wait_index = atomic_read(&hctx->wait_index); - bs = &bt->bs[wait_index]; - bt_index_atomic_inc(&hctx->wait_index); - return bs; -} - static int bt_get(struct blk_mq_alloc_data *data, - struct blk_mq_bitmap_tags *bt, - struct blk_mq_hw_ctx *hctx, - unsigned int *last_tag, struct blk_mq_tags *tags) + struct sbitmap_queue *bt, + struct blk_mq_hw_ctx *hctx, + unsigned int *last_tag, struct blk_mq_tags *tags) { - struct bt_wait_state *bs; + struct sbq_wait_state *ws; DEFINE_WAIT(wait); int tag; @@ -271,9 +133,9 @@ static int bt_get(struct blk_mq_alloc_data *data, if (data->flags & BLK_MQ_REQ_NOWAIT) return -1; - bs = bt_wait_ptr(bt, hctx); + ws = bt_wait_ptr(bt, hctx); do { - prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE); + prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE); tag = __bt_get(hctx, bt, last_tag, tags); if (tag != -1) @@ -310,11 +172,11 @@ static int bt_get(struct blk_mq_alloc_data *data, hctx = data->hctx; bt = &hctx->tags->bitmap_tags; } - finish_wait(&bs->wait, &wait); - bs = bt_wait_ptr(bt, hctx); + finish_wait(&ws->wait, &wait); + ws = bt_wait_ptr(bt, hctx); } while (1); - finish_wait(&bs->wait, &wait); + finish_wait(&ws->wait, &wait); return tag; } @@ -354,53 +216,6 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data) return __blk_mq_get_tag(data); } -static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt) -{ - int i, wake_index; - - wake_index = atomic_read(&bt->wake_index); - for (i = 0; i < BT_WAIT_QUEUES; i++) { - struct bt_wait_state *bs = &bt->bs[wake_index]; - - if (waitqueue_active(&bs->wait)) { - int o = atomic_read(&bt->wake_index); - if (wake_index != o) - atomic_cmpxchg(&bt->wake_index, o, wake_index); - - return bs; - } - - wake_index = bt_index_inc(wake_index); - } - - return NULL; -} - -static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag) -{ - const int index = TAG_TO_INDEX(bt, tag); - struct bt_wait_state *bs; - int wait_cnt; - - clear_bit(TAG_TO_BIT(bt, tag), &bt->map[index].word); - - /* Ensure that the wait list checks occur after clear_bit(). */ - smp_mb(); - - bs = bt_wake_ptr(bt); - if (!bs) - return; - - wait_cnt = atomic_dec_return(&bs->wait_cnt); - if (unlikely(wait_cnt < 0)) - wait_cnt = atomic_inc_return(&bs->wait_cnt); - if (wait_cnt == 0) { - atomic_add(bt->wake_cnt, &bs->wait_cnt); - bt_index_atomic_inc(&bt->wake_index); - wake_up(&bs->wait); - } -} - void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, unsigned int *last_tag) { @@ -410,67 +225,94 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, const int real_tag = tag - tags->nr_reserved_tags; BUG_ON(real_tag >= tags->nr_tags); - bt_clear_tag(&tags->bitmap_tags, real_tag); + sbitmap_queue_clear(&tags->bitmap_tags, real_tag); if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO)) *last_tag = real_tag; } else { BUG_ON(tag >= tags->nr_reserved_tags); - bt_clear_tag(&tags->breserved_tags, tag); + sbitmap_queue_clear(&tags->breserved_tags, tag); } } -static void bt_for_each(struct blk_mq_hw_ctx *hctx, - struct blk_mq_bitmap_tags *bt, unsigned int off, - busy_iter_fn *fn, void *data, bool reserved) +struct bt_iter_data { + struct blk_mq_hw_ctx *hctx; + busy_iter_fn *fn; + void *data; + bool reserved; +}; + +static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) { + struct bt_iter_data *iter_data = data; + struct blk_mq_hw_ctx *hctx = iter_data->hctx; + struct blk_mq_tags *tags = hctx->tags; + bool reserved = iter_data->reserved; struct request *rq; - int bit, i; - for (i = 0; i < bt->map_nr; i++) { - struct blk_align_bitmap *bm = &bt->map[i]; + if (!reserved) + bitnr += tags->nr_reserved_tags; + rq = tags->rqs[bitnr]; - for (bit = find_first_bit(&bm->word, bm->depth); - bit < bm->depth; - bit = find_next_bit(&bm->word, bm->depth, bit + 1)) { - rq = hctx->tags->rqs[off + bit]; - if (rq->q == hctx->queue) - fn(hctx, rq, data, reserved); - } + if (rq->q == hctx->queue) + iter_data->fn(hctx, rq, iter_data->data, reserved); + return true; +} - off += (1 << bt->bits_per_word); - } +static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt, + busy_iter_fn *fn, void *data, bool reserved) +{ + struct bt_iter_data iter_data = { + .hctx = hctx, + .fn = fn, + .data = data, + .reserved = reserved, + }; + + sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data); } -static void bt_tags_for_each(struct blk_mq_tags *tags, - struct blk_mq_bitmap_tags *bt, unsigned int off, - busy_tag_iter_fn *fn, void *data, bool reserved) +struct bt_tags_iter_data { + struct blk_mq_tags *tags; + busy_tag_iter_fn *fn; + void *data; + bool reserved; +}; + +static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) { + struct bt_tags_iter_data *iter_data = data; + struct blk_mq_tags *tags = iter_data->tags; + bool reserved = iter_data->reserved; struct request *rq; - int bit, i; - if (!tags->rqs) - return; - for (i = 0; i < bt->map_nr; i++) { - struct blk_align_bitmap *bm = &bt->map[i]; - - for (bit = find_first_bit(&bm->word, bm->depth); - bit < bm->depth; - bit = find_next_bit(&bm->word, bm->depth, bit + 1)) { - rq = tags->rqs[off + bit]; - fn(rq, data, reserved); - } + if (!reserved) + bitnr += tags->nr_reserved_tags; + rq = tags->rqs[bitnr]; - off += (1 << bt->bits_per_word); - } + iter_data->fn(rq, iter_data->data, reserved); + return true; +} + +static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt, + busy_tag_iter_fn *fn, void *data, bool reserved) +{ + struct bt_tags_iter_data iter_data = { + .tags = tags, + .fn = fn, + .data = data, + .reserved = reserved, + }; + + if (tags->rqs) + sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data); } static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn, void *priv) { if (tags->nr_reserved_tags) - bt_tags_for_each(tags, &tags->breserved_tags, 0, fn, priv, true); - bt_tags_for_each(tags, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv, - false); + bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true); + bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false); } void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, @@ -529,107 +371,20 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, continue; if (tags->nr_reserved_tags) - bt_for_each(hctx, &tags->breserved_tags, 0, fn, priv, true); - bt_for_each(hctx, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv, - false); - } - -} - -static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt) -{ - unsigned int i, used; - - for (i = 0, used = 0; i < bt->map_nr; i++) { - struct blk_align_bitmap *bm = &bt->map[i]; - - used += bitmap_weight(&bm->word, bm->depth); + bt_for_each(hctx, &tags->breserved_tags, fn, priv, true); + bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false); } - return bt->depth - used; } -static void bt_update_count(struct blk_mq_bitmap_tags *bt, - unsigned int depth) +static unsigned int bt_unused_tags(const struct sbitmap_queue *bt) { - unsigned int tags_per_word = 1U << bt->bits_per_word; - unsigned int map_depth = depth; - - if (depth) { - int i; - - for (i = 0; i < bt->map_nr; i++) { - bt->map[i].depth = min(map_depth, tags_per_word); - map_depth -= bt->map[i].depth; - } - } - - bt->wake_cnt = BT_WAIT_BATCH; - if (bt->wake_cnt > depth / BT_WAIT_QUEUES) - bt->wake_cnt = max(1U, depth / BT_WAIT_QUEUES); - - bt->depth = depth; + return bt->sb.depth - sbitmap_weight(&bt->sb); } -static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth, - int node, bool reserved) +static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth, int node) { - int i; - - bt->bits_per_word = ilog2(BITS_PER_LONG); - - /* - * Depth can be zero for reserved tags, that's not a failure - * condition. - */ - if (depth) { - unsigned int nr, tags_per_word; - - tags_per_word = (1 << bt->bits_per_word); - - /* - * If the tag space is small, shrink the number of tags - * per word so we spread over a few cachelines, at least. - * If less than 4 tags, just forget about it, it's not - * going to work optimally anyway. - */ - if (depth >= 4) { - while (tags_per_word * 4 > depth) { - bt->bits_per_word--; - tags_per_word = (1 << bt->bits_per_word); - } - } - - nr = ALIGN(depth, tags_per_word) / tags_per_word; - bt->map = kzalloc_node(nr * sizeof(struct blk_align_bitmap), - GFP_KERNEL, node); - if (!bt->map) - return -ENOMEM; - - bt->map_nr = nr; - } - - bt->bs = kzalloc(BT_WAIT_QUEUES * sizeof(*bt->bs), GFP_KERNEL); - if (!bt->bs) { - kfree(bt->map); - bt->map = NULL; - return -ENOMEM; - } - - bt_update_count(bt, depth); - - for (i = 0; i < BT_WAIT_QUEUES; i++) { - init_waitqueue_head(&bt->bs[i].wait); - atomic_set(&bt->bs[i].wait_cnt, bt->wake_cnt); - } - - return 0; -} - -static void bt_free(struct blk_mq_bitmap_tags *bt) -{ - kfree(bt->map); - kfree(bt->bs); + return sbitmap_queue_init_node(bt, depth, -1, GFP_KERNEL, node); } static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags, @@ -639,14 +394,15 @@ static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags, tags->alloc_policy = alloc_policy; - if (bt_alloc(&tags->bitmap_tags, depth, node, false)) - goto enomem; - if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true)) - goto enomem; + if (bt_alloc(&tags->bitmap_tags, depth, node)) + goto free_tags; + if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node)) + goto free_bitmap_tags; return tags; -enomem: - bt_free(&tags->bitmap_tags); +free_bitmap_tags: + sbitmap_queue_free(&tags->bitmap_tags); +free_tags: kfree(tags); return NULL; } @@ -679,8 +435,8 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, void blk_mq_free_tags(struct blk_mq_tags *tags) { - bt_free(&tags->bitmap_tags); - bt_free(&tags->breserved_tags); + sbitmap_queue_free(&tags->bitmap_tags); + sbitmap_queue_free(&tags->breserved_tags); free_cpumask_var(tags->cpumask); kfree(tags); } @@ -702,7 +458,8 @@ int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth) * Don't need (or can't) update reserved tags here, they remain * static and should never need resizing. */ - bt_update_count(&tags->bitmap_tags, tdepth); + sbitmap_queue_resize(&tags->bitmap_tags, tdepth); + blk_mq_tag_wakeup_all(tags, false); return 0; } @@ -746,7 +503,7 @@ ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page) page += sprintf(page, "nr_tags=%u, reserved_tags=%u, " "bits_per_word=%u\n", tags->nr_tags, tags->nr_reserved_tags, - tags->bitmap_tags.bits_per_word); + 1U << tags->bitmap_tags.sb.shift); free = bt_unused_tags(&tags->bitmap_tags); res = bt_unused_tags(&tags->breserved_tags); diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index d468a79f2c4a..3215c08c63cc 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -3,31 +3,6 @@ #include "blk-mq.h" -enum { - BT_WAIT_QUEUES = 8, - BT_WAIT_BATCH = 8, -}; - -struct bt_wait_state { - atomic_t wait_cnt; - wait_queue_head_t wait; -} ____cacheline_aligned_in_smp; - -#define TAG_TO_INDEX(bt, tag) ((tag) >> (bt)->bits_per_word) -#define TAG_TO_BIT(bt, tag) ((tag) & ((1 << (bt)->bits_per_word) - 1)) - -struct blk_mq_bitmap_tags { - unsigned int depth; - unsigned int wake_cnt; - unsigned int bits_per_word; - - unsigned int map_nr; - struct blk_align_bitmap *map; - - atomic_t wake_index; - struct bt_wait_state *bs; -}; - /* * Tag address space map. */ @@ -37,8 +12,8 @@ struct blk_mq_tags { atomic_t active_queues; - struct blk_mq_bitmap_tags bitmap_tags; - struct blk_mq_bitmap_tags breserved_tags; + struct sbitmap_queue bitmap_tags; + struct sbitmap_queue breserved_tags; struct request **rqs; struct list_head page_list; @@ -61,6 +36,14 @@ extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool); void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, void *priv); +static inline struct sbq_wait_state *bt_wait_ptr(struct sbitmap_queue *bt, + struct blk_mq_hw_ctx *hctx) +{ + if (!hctx) + return &bt->ws[0]; + return sbq_wait_ptr(bt, &hctx->wait_index); +} + enum { BLK_MQ_TAG_CACHE_MIN = 1, BLK_MQ_TAG_CACHE_MAX = 64, diff --git a/block/blk-mq.c b/block/blk-mq.c index 0cb93625d812..6603be18064e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -41,42 +41,23 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx); */ static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx) { - unsigned int i; - - for (i = 0; i < hctx->ctx_map.size; i++) - if (hctx->ctx_map.map[i].word) - return true; - - return false; -} - -static inline struct blk_align_bitmap *get_bm(struct blk_mq_hw_ctx *hctx, - struct blk_mq_ctx *ctx) -{ - return &hctx->ctx_map.map[ctx->index_hw / hctx->ctx_map.bits_per_word]; + return sbitmap_any_bit_set(&hctx->ctx_map); } -#define CTX_TO_BIT(hctx, ctx) \ - ((ctx)->index_hw & ((hctx)->ctx_map.bits_per_word - 1)) - /* * Mark this ctx as having pending work in this hardware queue */ static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx) { - struct blk_align_bitmap *bm = get_bm(hctx, ctx); - - if (!test_bit(CTX_TO_BIT(hctx, ctx), &bm->word)) - set_bit(CTX_TO_BIT(hctx, ctx), &bm->word); + if (!sbitmap_test_bit(&hctx->ctx_map, ctx->index_hw)) + sbitmap_set_bit(&hctx->ctx_map, ctx->index_hw); } static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx) { - struct blk_align_bitmap *bm = get_bm(hctx, ctx); - - clear_bit(CTX_TO_BIT(hctx, ctx), &bm->word); + sbitmap_clear_bit(&hctx->ctx_map, ctx->index_hw); } void blk_mq_freeze_queue_start(struct request_queue *q) @@ -755,38 +736,36 @@ static bool blk_mq_attempt_merge(struct request_queue *q, return false; } +struct flush_busy_ctx_data { + struct blk_mq_hw_ctx *hctx; + struct list_head *list; +}; + +static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data) +{ + struct flush_busy_ctx_data *flush_data = data; + struct blk_mq_hw_ctx *hctx = flush_data->hctx; + struct blk_mq_ctx *ctx = hctx->ctxs[bitnr]; + + sbitmap_clear_bit(sb, bitnr); + spin_lock(&ctx->lock); + list_splice_tail_init(&ctx->rq_list, flush_data->list); + spin_unlock(&ctx->lock); + return true; +} + /* * Process software queues that have been marked busy, splicing them * to the for-dispatch */ static void flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list) { - struct blk_mq_ctx *ctx; - int i; - - for (i = 0; i < hctx->ctx_map.size; i++) { - struct blk_align_bitmap *bm = &hctx->ctx_map.map[i]; - unsigned int off, bit; - - if (!bm->word) - continue; - - bit = 0; - off = i * hctx->ctx_map.bits_per_word; - do { - bit = find_next_bit(&bm->word, bm->depth, bit); - if (bit >= bm->depth) - break; - - ctx = hctx->ctxs[bit + off]; - clear_bit(bit, &bm->word); - spin_lock(&ctx->lock); - list_splice_tail_init(&ctx->rq_list, list); - spin_unlock(&ctx->lock); + struct flush_busy_ctx_data data = { + .hctx = hctx, + .list = list, + }; - bit++; - } while (1); - } + sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data); } static inline unsigned int queued_to_index(unsigned int queued) @@ -1609,32 +1588,6 @@ fail: return NULL; } -static void blk_mq_free_bitmap(struct blk_mq_ctxmap *bitmap) -{ - kfree(bitmap->map); -} - -static int blk_mq_alloc_bitmap(struct blk_mq_ctxmap *bitmap, int node) -{ - unsigned int bpw = 8, total, num_maps, i; - - bitmap->bits_per_word = bpw; - - num_maps = ALIGN(nr_cpu_ids, bpw) / bpw; - bitmap->map = kzalloc_node(num_maps * sizeof(struct blk_align_bitmap), - GFP_KERNEL, node); - if (!bitmap->map) - return -ENOMEM; - - total = nr_cpu_ids; - for (i = 0; i < num_maps; i++) { - bitmap->map[i].depth = min(total, bitmap->bits_per_word); - total -= bitmap->map[i].depth; - } - - return 0; -} - /* * 'cpu' is going away. splice any existing rq_list entries from this * software queue to the hw queue dispatch list, and ensure that it @@ -1700,7 +1653,7 @@ static void blk_mq_exit_hctx(struct request_queue *q, blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier); blk_free_flush_queue(hctx->fq); - blk_mq_free_bitmap(&hctx->ctx_map); + sbitmap_free(&hctx->ctx_map); } static void blk_mq_exit_hw_queues(struct request_queue *q, @@ -1760,7 +1713,8 @@ static int blk_mq_init_hctx(struct request_queue *q, if (!hctx->ctxs) goto unregister_cpu_notifier; - if (blk_mq_alloc_bitmap(&hctx->ctx_map, node)) + if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8), GFP_KERNEL, + node)) goto free_ctxs; hctx->nr_ctx = 0; @@ -1787,7 +1741,7 @@ static int blk_mq_init_hctx(struct request_queue *q, if (set->ops->exit_hctx) set->ops->exit_hctx(hctx, hctx_idx); free_bitmap: - blk_mq_free_bitmap(&hctx->ctx_map); + sbitmap_free(&hctx->ctx_map); free_ctxs: kfree(hctx->ctxs); unregister_cpu_notifier: @@ -1863,8 +1817,6 @@ static void blk_mq_map_swqueue(struct request_queue *q, mutex_unlock(&q->sysfs_lock); queue_for_each_hw_ctx(q, hctx, i) { - struct blk_mq_ctxmap *map = &hctx->ctx_map; - /* * If no software queues are mapped to this hardware queue, * disable it and free the request entries. @@ -1890,7 +1842,7 @@ static void blk_mq_map_swqueue(struct request_queue *q, * This is more accurate and more efficient than looping * over all possibly mapped software queues. */ - map->size = DIV_ROUND_UP(hctx->nr_ctx, map->bits_per_word); + sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx); /* * Initialize batch roundrobin counts diff --git a/block/blk-mq.h b/block/blk-mq.h index 9087b11037b7..71831f970fd3 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -63,15 +63,6 @@ extern void blk_mq_rq_timed_out(struct request *req, bool reserved); void blk_mq_release(struct request_queue *q); -/* - * Basic implementation of sparser bitmap, allowing the user to spread - * the bits over more cachelines. - */ -struct blk_align_bitmap { - unsigned long word; - unsigned long depth; -} ____cacheline_aligned_in_smp; - static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q, unsigned int cpu) { diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 60ef14cbcd2d..2575779cf13f 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -2,6 +2,7 @@ #define BLK_MQ_H #include +#include struct blk_mq_tags; struct blk_flush_queue; @@ -12,12 +13,6 @@ struct blk_mq_cpu_notifier { int (*notify)(void *data, unsigned long action, unsigned int cpu); }; -struct blk_mq_ctxmap { - unsigned int size; - unsigned int bits_per_word; - struct blk_align_bitmap *map; -}; - struct blk_mq_hw_ctx { struct { spinlock_t lock; @@ -37,7 +32,7 @@ struct blk_mq_hw_ctx { void *driver_data; - struct blk_mq_ctxmap ctx_map; + struct sbitmap ctx_map; struct blk_mq_ctx **ctxs; unsigned int nr_ctx; diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h new file mode 100644 index 000000000000..1a3b836042e1 --- /dev/null +++ b/include/linux/sbitmap.h @@ -0,0 +1,327 @@ +/* + * Fast and scalable bitmaps. + * + * Copyright (C) 2016 Facebook + * Copyright (C) 2013-2014 Jens Axboe + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public + * License v2 as published by the Free Software Foundation. + * + * 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, see . + */ + +#ifndef __LINUX_SCALE_BITMAP_H +#define __LINUX_SCALE_BITMAP_H + +#include +#include + +/** + * struct sbitmap_word - Word in a &struct sbitmap. + */ +struct sbitmap_word { + /** + * @word: The bitmap word itself. + */ + unsigned long word; + + /** + * @depth: Number of bits being used in @word. + */ + unsigned long depth; +} ____cacheline_aligned_in_smp; + +/** + * struct sbitmap - Scalable bitmap. + * + * A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This + * trades off higher memory usage for better scalability. + */ +struct sbitmap { + /** + * @depth: Number of bits used in the whole bitmap. + */ + unsigned int depth; + + /** + * @shift: log2(number of bits used per word) + */ + unsigned int shift; + + /** + * @map_nr: Number of words (cachelines) being used for the bitmap. + */ + unsigned int map_nr; + + /** + * @map: Allocated bitmap. + */ + struct sbitmap_word *map; +}; + +#define SBQ_WAIT_QUEUES 8 +#define SBQ_WAKE_BATCH 8 + +/** + * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue. + */ +struct sbq_wait_state { + /** + * @wait_cnt: Number of frees remaining before we wake up. + */ + atomic_t wait_cnt; + + /** + * @wait: Wait queue. + */ + wait_queue_head_t wait; +} ____cacheline_aligned_in_smp; + +/** + * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free + * bits. + * + * A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to + * avoid contention on the wait queue spinlock. This ensures that we don't hit a + * scalability wall when we run out of free bits and have to start putting tasks + * to sleep. + */ +struct sbitmap_queue { + /** + * @sb: Scalable bitmap. + */ + struct sbitmap sb; + + /** + * @wake_batch: Number of bits which must be freed before we wake up any + * waiters. + */ + unsigned int wake_batch; + + /** + * @wake_index: Next wait queue in @ws to wake up. + */ + atomic_t wake_index; + + /** + * @ws: Wait queues. + */ + struct sbq_wait_state *ws; +}; + +/** + * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node. + * @sb: Bitmap to initialize. + * @depth: Number of bits to allocate. + * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if + * given, a good default is chosen. + * @flags: Allocation flags. + * @node: Memory node to allocate on. + * + * Return: Zero on success or negative errno on failure. + */ +int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, + gfp_t flags, int node); + +/** + * sbitmap_free() - Free memory used by a &struct sbitmap. + * @sb: Bitmap to free. + */ +static inline void sbitmap_free(struct sbitmap *sb) +{ + kfree(sb->map); + sb->map = NULL; +} + +/** + * sbitmap_resize() - Resize a &struct sbitmap. + * @sb: Bitmap to resize. + * @depth: New number of bits to resize to. + * + * Doesn't reallocate anything. It's up to the caller to ensure that the new + * depth doesn't exceed the depth that the sb was initialized with. + */ +void sbitmap_resize(struct sbitmap *sb, unsigned int depth); + +/** + * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap. + * @sb: Bitmap to allocate from. + * @alloc_hint: Hint for where to start searching for a free bit. + * @round_robin: If true, be stricter about allocation order; always allocate + * starting from the last allocated bit. This is less efficient + * than the default behavior (false). + * + * Return: Non-negative allocated bit number if successful, -1 otherwise. + */ +int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin); + +/** + * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap. + * @sb: Bitmap to check. + * + * Return: true if any bit in the bitmap is set, false otherwise. + */ +bool sbitmap_any_bit_set(const struct sbitmap *sb); + +/** + * sbitmap_any_bit_clear() - Check for an unset bit in a &struct + * sbitmap. + * @sb: Bitmap to check. + * + * Return: true if any bit in the bitmap is clear, false otherwise. + */ +bool sbitmap_any_bit_clear(const struct sbitmap *sb); + +typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *); + +/** + * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap. + * @sb: Bitmap to iterate over. + * @fn: Callback. Should return true to continue or false to break early. + * @data: Pointer to pass to callback. + * + * This is inline even though it's non-trivial so that the function calls to the + * callback will hopefully get optimized away. + */ +static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn, + void *data) +{ + unsigned int i; + + for (i = 0; i < sb->map_nr; i++) { + struct sbitmap_word *word = &sb->map[i]; + unsigned int off, nr; + + if (!word->word) + continue; + + nr = 0; + off = i << sb->shift; + while (1) { + nr = find_next_bit(&word->word, word->depth, nr); + if (nr >= word->depth) + break; + + if (!fn(sb, off + nr, data)) + return; + + nr++; + } + } +} + +#define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift) +#define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U)) + +static inline unsigned long *__sbitmap_word(struct sbitmap *sb, + unsigned int bitnr) +{ + return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word; +} + +/* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */ + +static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr) +{ + set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); +} + +static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr) +{ + clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); +} + +static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr) +{ + return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); +} + +unsigned int sbitmap_weight(const struct sbitmap *sb); + +/** + * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific + * memory node. + * @sbq: Bitmap queue to initialize. + * @depth: See sbitmap_init_node(). + * @shift: See sbitmap_init_node(). + * @flags: Allocation flags. + * @node: Memory node to allocate on. + * + * Return: Zero on success or negative errno on failure. + */ +int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, + int shift, gfp_t flags, int node); + +/** + * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue. + * + * @sbq: Bitmap queue to free. + */ +static inline void sbitmap_queue_free(struct sbitmap_queue *sbq) +{ + kfree(sbq->ws); + sbitmap_free(&sbq->sb); +} + +/** + * sbitmap_queue_resize() - Resize a &struct sbitmap_queue. + * @sbq: Bitmap queue to resize. + * @depth: New number of bits to resize to. + * + * Like sbitmap_resize(), this doesn't reallocate anything. It has to do + * some extra work on the &struct sbitmap_queue, so it's not safe to just + * resize the underlying &struct sbitmap. + */ +void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth); + +/** + * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a + * &struct sbitmap_queue. + * @sbq: Bitmap to free from. + * @nr: Bit number to free. + */ +void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr); + +static inline int sbq_index_inc(int index) +{ + return (index + 1) & (SBQ_WAIT_QUEUES - 1); +} + +static inline void sbq_index_atomic_inc(atomic_t *index) +{ + int old = atomic_read(index); + int new = sbq_index_inc(old); + atomic_cmpxchg(index, old, new); +} + +/** + * sbq_wait_ptr() - Get the next wait queue to use for a &struct + * sbitmap_queue. + * @sbq: Bitmap queue to wait on. + * @wait_index: A counter per "user" of @sbq. + */ +static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq, + atomic_t *wait_index) +{ + struct sbq_wait_state *ws; + + ws = &sbq->ws[atomic_read(wait_index)]; + sbq_index_atomic_inc(wait_index); + return ws; +} + +/** + * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct + * sbitmap_queue. + * @sbq: Bitmap queue to wake up. + */ +void sbitmap_queue_wake_all(struct sbitmap_queue *sbq); + +#endif /* __LINUX_SCALE_BITMAP_H */ diff --git a/lib/Kconfig b/lib/Kconfig index d79909dc01ec..942fb8091a86 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -550,4 +550,7 @@ config STACKDEPOT bool select STACKTRACE +config SBITMAP + bool + endmenu diff --git a/lib/Makefile b/lib/Makefile index cfa68eb269e4..2cbfd2904994 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -228,3 +228,5 @@ obj-$(CONFIG_UCS2_STRING) += ucs2_string.o obj-$(CONFIG_UBSAN) += ubsan.o UBSAN_SANITIZE_ubsan.o := n + +obj-$(CONFIG_SBITMAP) += sbitmap.o diff --git a/lib/sbitmap.c b/lib/sbitmap.c new file mode 100644 index 000000000000..dfc084ac6937 --- /dev/null +++ b/lib/sbitmap.c @@ -0,0 +1,301 @@ +/* + * Copyright (C) 2016 Facebook + * Copyright (C) 2013-2014 Jens Axboe + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public + * License v2 as published by the Free Software Foundation. + * + * 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, see . + */ + +#include + +int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, + gfp_t flags, int node) +{ + unsigned int bits_per_word; + unsigned int i; + + if (shift < 0) { + shift = ilog2(BITS_PER_LONG); + /* + * If the bitmap is small, shrink the number of bits per word so + * we spread over a few cachelines, at least. If less than 4 + * bits, just forget about it, it's not going to work optimally + * anyway. + */ + if (depth >= 4) { + while ((4U << shift) > depth) + shift--; + } + } + bits_per_word = 1U << shift; + if (bits_per_word > BITS_PER_LONG) + return -EINVAL; + + sb->shift = shift; + sb->depth = depth; + sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word); + + if (depth == 0) { + sb->map = NULL; + return 0; + } + + sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node); + if (!sb->map) + return -ENOMEM; + + for (i = 0; i < sb->map_nr; i++) { + sb->map[i].depth = min(depth, bits_per_word); + depth -= sb->map[i].depth; + } + return 0; +} +EXPORT_SYMBOL_GPL(sbitmap_init_node); + +void sbitmap_resize(struct sbitmap *sb, unsigned int depth) +{ + unsigned int bits_per_word = 1U << sb->shift; + unsigned int i; + + sb->depth = depth; + sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word); + + for (i = 0; i < sb->map_nr; i++) { + sb->map[i].depth = min(depth, bits_per_word); + depth -= sb->map[i].depth; + } +} +EXPORT_SYMBOL_GPL(sbitmap_resize); + +static int __sbitmap_get_word(struct sbitmap_word *word, unsigned int hint, + bool wrap) +{ + unsigned int orig_hint = hint; + int nr; + + while (1) { + nr = find_next_zero_bit(&word->word, word->depth, hint); + if (unlikely(nr >= word->depth)) { + /* + * We started with an offset, and we didn't reset the + * offset to 0 in a failure case, so start from 0 to + * exhaust the map. + */ + if (orig_hint && hint && wrap) { + hint = orig_hint = 0; + continue; + } + return -1; + } + + if (!test_and_set_bit(nr, &word->word)) + break; + + hint = nr + 1; + if (hint >= word->depth - 1) + hint = 0; + } + + return nr; +} + +int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin) +{ + unsigned int i, index; + int nr = -1; + + index = SB_NR_TO_INDEX(sb, alloc_hint); + + for (i = 0; i < sb->map_nr; i++) { + nr = __sbitmap_get_word(&sb->map[index], + SB_NR_TO_BIT(sb, alloc_hint), + !round_robin); + if (nr != -1) { + nr += index << sb->shift; + break; + } + + /* Jump to next index. */ + index++; + alloc_hint = index << sb->shift; + + if (index >= sb->map_nr) { + index = 0; + alloc_hint = 0; + } + } + + return nr; +} +EXPORT_SYMBOL_GPL(sbitmap_get); + +bool sbitmap_any_bit_set(const struct sbitmap *sb) +{ + unsigned int i; + + for (i = 0; i < sb->map_nr; i++) { + if (sb->map[i].word) + return true; + } + return false; +} +EXPORT_SYMBOL_GPL(sbitmap_any_bit_set); + +bool sbitmap_any_bit_clear(const struct sbitmap *sb) +{ + unsigned int i; + + for (i = 0; i < sb->map_nr; i++) { + const struct sbitmap_word *word = &sb->map[i]; + unsigned long ret; + + ret = find_first_zero_bit(&word->word, word->depth); + if (ret < word->depth) + return true; + } + return false; +} +EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear); + +unsigned int sbitmap_weight(const struct sbitmap *sb) +{ + unsigned int i, weight; + + for (i = 0; i < sb->map_nr; i++) { + const struct sbitmap_word *word = &sb->map[i]; + + weight += bitmap_weight(&word->word, word->depth); + } + return weight; +} +EXPORT_SYMBOL_GPL(sbitmap_weight); + +static unsigned int sbq_calc_wake_batch(unsigned int depth) +{ + unsigned int wake_batch; + + /* + * For each batch, we wake up one queue. We need to make sure that our + * batch size is small enough that the full depth of the bitmap is + * enough to wake up all of the queues. + */ + wake_batch = SBQ_WAKE_BATCH; + if (wake_batch > depth / SBQ_WAIT_QUEUES) + wake_batch = max(1U, depth / SBQ_WAIT_QUEUES); + + return wake_batch; +} + +int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, + int shift, gfp_t flags, int node) +{ + int ret; + int i; + + ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node); + if (ret) + return ret; + + sbq->wake_batch = sbq_calc_wake_batch(depth); + atomic_set(&sbq->wake_index, 0); + + sbq->ws = kzalloc(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags); + if (!sbq->ws) { + sbitmap_free(&sbq->sb); + return -ENOMEM; + } + + for (i = 0; i < SBQ_WAIT_QUEUES; i++) { + init_waitqueue_head(&sbq->ws[i].wait); + atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch); + } + return 0; +} +EXPORT_SYMBOL_GPL(sbitmap_queue_init_node); + +void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth) +{ + sbq->wake_batch = sbq_calc_wake_batch(depth); + sbitmap_resize(&sbq->sb, depth); +} +EXPORT_SYMBOL_GPL(sbitmap_queue_resize); + +static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq) +{ + int i, wake_index; + + wake_index = atomic_read(&sbq->wake_index); + for (i = 0; i < SBQ_WAIT_QUEUES; i++) { + struct sbq_wait_state *ws = &sbq->ws[wake_index]; + + if (waitqueue_active(&ws->wait)) { + int o = atomic_read(&sbq->wake_index); + + if (wake_index != o) + atomic_cmpxchg(&sbq->wake_index, o, wake_index); + return ws; + } + + wake_index = sbq_index_inc(wake_index); + } + + return NULL; +} + +static void sbq_wake_up(struct sbitmap_queue *sbq) +{ + struct sbq_wait_state *ws; + int wait_cnt; + + /* Ensure that the wait list checks occur after clear_bit(). */ + smp_mb(); + + ws = sbq_wake_ptr(sbq); + if (!ws) + return; + + wait_cnt = atomic_dec_return(&ws->wait_cnt); + if (unlikely(wait_cnt < 0)) + wait_cnt = atomic_inc_return(&ws->wait_cnt); + if (wait_cnt == 0) { + atomic_add(sbq->wake_batch, &ws->wait_cnt); + sbq_index_atomic_inc(&sbq->wake_index); + wake_up(&ws->wait); + } +} + +void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr) +{ + sbitmap_clear_bit(&sbq->sb, nr); + sbq_wake_up(sbq); +} +EXPORT_SYMBOL_GPL(sbitmap_queue_clear); + +void sbitmap_queue_wake_all(struct sbitmap_queue *sbq) +{ + int i, wake_index; + + /* + * Make sure all changes prior to this are visible from other CPUs. + */ + smp_mb(); + wake_index = atomic_read(&sbq->wake_index); + for (i = 0; i < SBQ_WAIT_QUEUES; i++) { + struct sbq_wait_state *ws = &sbq->ws[wake_index]; + + if (waitqueue_active(&ws->wait)) + wake_up(&ws->wait); + + wake_index = sbq_index_inc(wake_index); + } +} +EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all); -- cgit v1.2.3 From 40aabb67464d5aad9ca3d2a5fedee56e2ff45aa0 Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Sat, 17 Sep 2016 01:28:23 -0700 Subject: sbitmap: push per-cpu last_tag into sbitmap_queue Allocating your own per-cpu allocation hint separately makes for an awkward API. Instead, allocate the per-cpu hint as part of the struct sbitmap_queue. There's no point for a struct sbitmap_queue without the cache, but you can still use a bare struct sbitmap. Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe --- block/blk-mq-tag.c | 53 ++++++++++++++++--------------------------------- block/blk-mq-tag.h | 3 ++- block/blk-mq.c | 2 +- block/blk-mq.h | 2 -- include/linux/sbitmap.h | 45 ++++++++++++++++++++++++++++++++++++++++- lib/sbitmap.c | 35 +++++++++++++++++++++++++++++++- 6 files changed, 98 insertions(+), 42 deletions(-) (limited to 'block') diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 2cbdecd594e9..c9a22dbbbda1 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -94,39 +94,21 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, #define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR) static int __bt_get(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt, - unsigned int *tag_cache, struct blk_mq_tags *tags) + struct blk_mq_tags *tags) { - unsigned int last_tag; - int tag; - if (!hctx_may_queue(hctx, bt)) return -1; - - last_tag = *tag_cache; - tag = sbitmap_get(&bt->sb, last_tag, BT_ALLOC_RR(tags)); - - if (tag == -1) { - *tag_cache = 0; - } else if (tag == last_tag || unlikely(BT_ALLOC_RR(tags))) { - last_tag = tag + 1; - if (last_tag >= bt->sb.depth - 1) - last_tag = 0; - *tag_cache = last_tag; - } - - return tag; + return __sbitmap_queue_get(bt, BT_ALLOC_RR(tags)); } -static int bt_get(struct blk_mq_alloc_data *data, - struct sbitmap_queue *bt, - struct blk_mq_hw_ctx *hctx, - unsigned int *last_tag, struct blk_mq_tags *tags) +static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt, + struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags) { struct sbq_wait_state *ws; DEFINE_WAIT(wait); int tag; - tag = __bt_get(hctx, bt, last_tag, tags); + tag = __bt_get(hctx, bt, tags); if (tag != -1) return tag; @@ -137,7 +119,7 @@ static int bt_get(struct blk_mq_alloc_data *data, do { prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE); - tag = __bt_get(hctx, bt, last_tag, tags); + tag = __bt_get(hctx, bt, tags); if (tag != -1) break; @@ -154,7 +136,7 @@ static int bt_get(struct blk_mq_alloc_data *data, * Retry tag allocation after running the hardware queue, * as running the queue may also have found completions. */ - tag = __bt_get(hctx, bt, last_tag, tags); + tag = __bt_get(hctx, bt, tags); if (tag != -1) break; @@ -168,7 +150,6 @@ static int bt_get(struct blk_mq_alloc_data *data, if (data->flags & BLK_MQ_REQ_RESERVED) { bt = &data->hctx->tags->breserved_tags; } else { - last_tag = &data->ctx->last_tag; hctx = data->hctx; bt = &hctx->tags->bitmap_tags; } @@ -185,7 +166,7 @@ static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data) int tag; tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx, - &data->ctx->last_tag, data->hctx->tags); + data->hctx->tags); if (tag >= 0) return tag + data->hctx->tags->nr_reserved_tags; @@ -194,15 +175,15 @@ static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data) static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data) { - int tag, zero = 0; + int tag; if (unlikely(!data->hctx->tags->nr_reserved_tags)) { WARN_ON_ONCE(1); return BLK_MQ_TAG_FAIL; } - tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero, - data->hctx->tags); + tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, + data->hctx->tags); if (tag < 0) return BLK_MQ_TAG_FAIL; @@ -216,8 +197,8 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data) return __blk_mq_get_tag(data); } -void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, - unsigned int *last_tag) +void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, + unsigned int tag) { struct blk_mq_tags *tags = hctx->tags; @@ -225,12 +206,12 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, const int real_tag = tag - tags->nr_reserved_tags; BUG_ON(real_tag >= tags->nr_tags); - sbitmap_queue_clear(&tags->bitmap_tags, real_tag); - if (likely(tags->alloc_policy == BLK_TAG_ALLOC_FIFO)) - *last_tag = real_tag; + sbitmap_queue_clear(&tags->bitmap_tags, real_tag, + BT_ALLOC_RR(tags), ctx->cpu); } else { BUG_ON(tag >= tags->nr_reserved_tags); - sbitmap_queue_clear(&tags->breserved_tags, tag); + sbitmap_queue_clear(&tags->breserved_tags, tag, + BT_ALLOC_RR(tags), ctx->cpu); } } diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index 3215c08c63cc..2b1d52ed82e0 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -27,7 +27,8 @@ extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int r extern void blk_mq_free_tags(struct blk_mq_tags *tags); extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data); -extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, unsigned int *last_tag); +extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, + unsigned int tag); extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags); extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page); extern void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *last_tag); diff --git a/block/blk-mq.c b/block/blk-mq.c index 6603be18064e..e0a69daddbd8 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -303,7 +303,7 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx, rq->cmd_flags = 0; clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags); - blk_mq_put_tag(hctx, tag, &ctx->last_tag); + blk_mq_put_tag(hctx, ctx, tag); blk_queue_exit(q); } diff --git a/block/blk-mq.h b/block/blk-mq.h index 71831f970fd3..9b15d2ef7f7b 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -12,8 +12,6 @@ struct blk_mq_ctx { unsigned int cpu; unsigned int index_hw; - unsigned int last_tag ____cacheline_aligned_in_smp; - /* incremented at dispatch time */ unsigned long rq_dispatched[2]; unsigned long rq_merged; diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h index 1a3b836042e1..6745545e0b22 100644 --- a/include/linux/sbitmap.h +++ b/include/linux/sbitmap.h @@ -99,6 +99,14 @@ struct sbitmap_queue { */ struct sbitmap sb; + /* + * @alloc_hint: Cache of last successfully allocated or freed bit. + * + * This is per-cpu, which allows multiple users to stick to different + * cachelines until the map is exhausted. + */ + unsigned int __percpu *alloc_hint; + /** * @wake_batch: Number of bits which must be freed before we wake up any * waiters. @@ -267,6 +275,7 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, static inline void sbitmap_queue_free(struct sbitmap_queue *sbq) { kfree(sbq->ws); + free_percpu(sbq->alloc_hint); sbitmap_free(&sbq->sb); } @@ -281,13 +290,47 @@ static inline void sbitmap_queue_free(struct sbitmap_queue *sbq) */ void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth); +/** + * __sbitmap_queue_get() - Try to allocate a free bit from a &struct + * sbitmap_queue with preemption already disabled. + * @sbq: Bitmap queue to allocate from. + * @round_robin: See sbitmap_get(). + * + * Return: Non-negative allocated bit number if successful, -1 otherwise. + */ +int __sbitmap_queue_get(struct sbitmap_queue *sbq, bool round_robin); + +/** + * sbitmap_queue_get() - Try to allocate a free bit from a &struct + * sbitmap_queue. + * @sbq: Bitmap queue to allocate from. + * @round_robin: See sbitmap_get(). + * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to + * sbitmap_queue_clear()). + * + * Return: Non-negative allocated bit number if successful, -1 otherwise. + */ +static inline int sbitmap_queue_get(struct sbitmap_queue *sbq, bool round_robin, + unsigned int *cpu) +{ + int nr; + + *cpu = get_cpu(); + nr = __sbitmap_queue_get(sbq, round_robin); + put_cpu(); + return nr; +} + /** * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a * &struct sbitmap_queue. * @sbq: Bitmap to free from. * @nr: Bit number to free. + * @round_robin: See sbitmap_get(). + * @cpu: CPU the bit was allocated on. */ -void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr); +void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, + bool round_robin, unsigned int cpu); static inline int sbq_index_inc(int index) { diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 4d8e97e470ee..1651ad9d5530 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -205,11 +205,18 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, if (ret) return ret; + sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags); + if (!sbq->alloc_hint) { + sbitmap_free(&sbq->sb); + return -ENOMEM; + } + sbq->wake_batch = sbq_calc_wake_batch(depth); atomic_set(&sbq->wake_index, 0); sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node); if (!sbq->ws) { + free_percpu(sbq->alloc_hint); sbitmap_free(&sbq->sb); return -ENOMEM; } @@ -229,6 +236,29 @@ void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth) } EXPORT_SYMBOL_GPL(sbitmap_queue_resize); +int __sbitmap_queue_get(struct sbitmap_queue *sbq, bool round_robin) +{ + unsigned int hint; + int nr; + + hint = this_cpu_read(*sbq->alloc_hint); + nr = sbitmap_get(&sbq->sb, hint, round_robin); + + if (nr == -1) { + /* If the map is full, a hint won't do us much good. */ + this_cpu_write(*sbq->alloc_hint, 0); + } else if (nr == hint || unlikely(round_robin)) { + /* Only update the hint if we used it. */ + hint = nr + 1; + if (hint >= sbq->sb.depth - 1) + hint = 0; + this_cpu_write(*sbq->alloc_hint, hint); + } + + return nr; +} +EXPORT_SYMBOL_GPL(__sbitmap_queue_get); + static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq) { int i, wake_index; @@ -273,10 +303,13 @@ static void sbq_wake_up(struct sbitmap_queue *sbq) } } -void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr) +void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, + bool round_robin, unsigned int cpu) { sbitmap_clear_bit(&sbq->sb, nr); sbq_wake_up(sbq); + if (likely(!round_robin)) + *per_cpu_ptr(sbq->alloc_hint, cpu) = nr; } EXPORT_SYMBOL_GPL(sbitmap_queue_clear); -- cgit v1.2.3 From f4a644db86669d938c71f19560aebf69d4720d63 Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Sat, 17 Sep 2016 01:28:24 -0700 Subject: sbitmap: push alloc policy into sbitmap_queue Again, there's no point in passing this in every time. Make it part of struct sbitmap_queue and clean up the API. Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe --- block/blk-mq-tag.c | 33 +++++++++++++++------------------ block/blk-mq-tag.h | 1 - include/linux/sbitmap.h | 19 +++++++++++-------- lib/sbitmap.c | 14 ++++++++------ 4 files changed, 34 insertions(+), 33 deletions(-) (limited to 'block') diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index c9a22dbbbda1..e1c2bedb0bf9 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -91,14 +91,11 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, return atomic_read(&hctx->nr_active) < depth; } -#define BT_ALLOC_RR(tags) (tags->alloc_policy == BLK_TAG_ALLOC_RR) - -static int __bt_get(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt, - struct blk_mq_tags *tags) +static int __bt_get(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt) { if (!hctx_may_queue(hctx, bt)) return -1; - return __sbitmap_queue_get(bt, BT_ALLOC_RR(tags)); + return __sbitmap_queue_get(bt); } static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt, @@ -108,7 +105,7 @@ static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt, DEFINE_WAIT(wait); int tag; - tag = __bt_get(hctx, bt, tags); + tag = __bt_get(hctx, bt); if (tag != -1) return tag; @@ -119,7 +116,7 @@ static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt, do { prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE); - tag = __bt_get(hctx, bt, tags); + tag = __bt_get(hctx, bt); if (tag != -1) break; @@ -136,7 +133,7 @@ static int bt_get(struct blk_mq_alloc_data *data, struct sbitmap_queue *bt, * Retry tag allocation after running the hardware queue, * as running the queue may also have found completions. */ - tag = __bt_get(hctx, bt, tags); + tag = __bt_get(hctx, bt); if (tag != -1) break; @@ -206,12 +203,10 @@ void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, const int real_tag = tag - tags->nr_reserved_tags; BUG_ON(real_tag >= tags->nr_tags); - sbitmap_queue_clear(&tags->bitmap_tags, real_tag, - BT_ALLOC_RR(tags), ctx->cpu); + sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu); } else { BUG_ON(tag >= tags->nr_reserved_tags); - sbitmap_queue_clear(&tags->breserved_tags, tag, - BT_ALLOC_RR(tags), ctx->cpu); + sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu); } } @@ -363,21 +358,23 @@ static unsigned int bt_unused_tags(const struct sbitmap_queue *bt) return bt->sb.depth - sbitmap_weight(&bt->sb); } -static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth, int node) +static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth, + bool round_robin, int node) { - return sbitmap_queue_init_node(bt, depth, -1, GFP_KERNEL, node); + return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL, + node); } static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags, int node, int alloc_policy) { unsigned int depth = tags->nr_tags - tags->nr_reserved_tags; + bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR; - tags->alloc_policy = alloc_policy; - - if (bt_alloc(&tags->bitmap_tags, depth, node)) + if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node)) goto free_tags; - if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node)) + if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin, + node)) goto free_bitmap_tags; return tags; diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index 2b1d52ed82e0..f90b850ce43d 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -18,7 +18,6 @@ struct blk_mq_tags { struct request **rqs; struct list_head page_list; - int alloc_policy; cpumask_var_t cpumask; }; diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h index 6745545e0b22..f017fd6e69c4 100644 --- a/include/linux/sbitmap.h +++ b/include/linux/sbitmap.h @@ -122,6 +122,11 @@ struct sbitmap_queue { * @ws: Wait queues. */ struct sbq_wait_state *ws; + + /** + * @round_robin: Allocate bits in strict round-robin order. + */ + bool round_robin; }; /** @@ -259,13 +264,14 @@ unsigned int sbitmap_weight(const struct sbitmap *sb); * @sbq: Bitmap queue to initialize. * @depth: See sbitmap_init_node(). * @shift: See sbitmap_init_node(). + * @round_robin: See sbitmap_get(). * @flags: Allocation flags. * @node: Memory node to allocate on. * * Return: Zero on success or negative errno on failure. */ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, - int shift, gfp_t flags, int node); + int shift, bool round_robin, gfp_t flags, int node); /** * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue. @@ -294,29 +300,27 @@ void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth); * __sbitmap_queue_get() - Try to allocate a free bit from a &struct * sbitmap_queue with preemption already disabled. * @sbq: Bitmap queue to allocate from. - * @round_robin: See sbitmap_get(). * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ -int __sbitmap_queue_get(struct sbitmap_queue *sbq, bool round_robin); +int __sbitmap_queue_get(struct sbitmap_queue *sbq); /** * sbitmap_queue_get() - Try to allocate a free bit from a &struct * sbitmap_queue. * @sbq: Bitmap queue to allocate from. - * @round_robin: See sbitmap_get(). * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to * sbitmap_queue_clear()). * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ -static inline int sbitmap_queue_get(struct sbitmap_queue *sbq, bool round_robin, +static inline int sbitmap_queue_get(struct sbitmap_queue *sbq, unsigned int *cpu) { int nr; *cpu = get_cpu(); - nr = __sbitmap_queue_get(sbq, round_robin); + nr = __sbitmap_queue_get(sbq); put_cpu(); return nr; } @@ -326,11 +330,10 @@ static inline int sbitmap_queue_get(struct sbitmap_queue *sbq, bool round_robin, * &struct sbitmap_queue. * @sbq: Bitmap to free from. * @nr: Bit number to free. - * @round_robin: See sbitmap_get(). * @cpu: CPU the bit was allocated on. */ void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, - bool round_robin, unsigned int cpu); + unsigned int cpu); static inline int sbq_index_inc(int index) { diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 1651ad9d5530..be55f744b771 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -196,7 +196,7 @@ static unsigned int sbq_calc_wake_batch(unsigned int depth) } int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, - int shift, gfp_t flags, int node) + int shift, bool round_robin, gfp_t flags, int node) { int ret; int i; @@ -225,6 +225,8 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, init_waitqueue_head(&sbq->ws[i].wait); atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch); } + + sbq->round_robin = round_robin; return 0; } EXPORT_SYMBOL_GPL(sbitmap_queue_init_node); @@ -236,18 +238,18 @@ void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth) } EXPORT_SYMBOL_GPL(sbitmap_queue_resize); -int __sbitmap_queue_get(struct sbitmap_queue *sbq, bool round_robin) +int __sbitmap_queue_get(struct sbitmap_queue *sbq) { unsigned int hint; int nr; hint = this_cpu_read(*sbq->alloc_hint); - nr = sbitmap_get(&sbq->sb, hint, round_robin); + nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin); if (nr == -1) { /* If the map is full, a hint won't do us much good. */ this_cpu_write(*sbq->alloc_hint, 0); - } else if (nr == hint || unlikely(round_robin)) { + } else if (nr == hint || unlikely(sbq->round_robin)) { /* Only update the hint if we used it. */ hint = nr + 1; if (hint >= sbq->sb.depth - 1) @@ -304,11 +306,11 @@ static void sbq_wake_up(struct sbitmap_queue *sbq) } void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, - bool round_robin, unsigned int cpu) + unsigned int cpu) { sbitmap_clear_bit(&sbq->sb, nr); sbq_wake_up(sbq); - if (likely(!round_robin)) + if (likely(!sbq->round_robin)) *per_cpu_ptr(sbq->alloc_hint, cpu) = nr; } EXPORT_SYMBOL_GPL(sbitmap_queue_clear); -- cgit v1.2.3 From 98d95416dbfaf4910caadfb4ddc75e4aacbdff8c Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Sat, 17 Sep 2016 01:28:25 -0700 Subject: sbitmap: randomize initial alloc_hint values In order to get good cache behavior from a sbitmap, we want each CPU to stick to its own cacheline(s) as much as possible. This might happen naturally as the bitmap gets filled up and the alloc_hint values spread out, but we really want this behavior from the start. blk-mq apparently intended to do this, but the code to do this was never wired up. Get rid of the dead code and make it part of the sbitmap library. Signed-off-by: Omar Sandoval Signed-off-by: Jens Axboe --- block/blk-mq-tag.c | 8 -------- block/blk-mq-tag.h | 1 - lib/sbitmap.c | 6 ++++++ 3 files changed, 6 insertions(+), 9 deletions(-) (limited to 'block') diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index e1c2bedb0bf9..cef618f6fc92 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -7,7 +7,6 @@ */ #include #include -#include #include #include "blk.h" @@ -419,13 +418,6 @@ void blk_mq_free_tags(struct blk_mq_tags *tags) kfree(tags); } -void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *tag) -{ - unsigned int depth = tags->nr_tags - tags->nr_reserved_tags; - - *tag = prandom_u32() % depth; -} - int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth) { tdepth -= tags->nr_reserved_tags; diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index f90b850ce43d..09f4cc0aaa84 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -30,7 +30,6 @@ extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, unsigned int tag); extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags); extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page); -extern void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *last_tag); extern int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int depth); extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool); void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, diff --git a/lib/sbitmap.c b/lib/sbitmap.c index be55f744b771..928b82a733f2 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -15,6 +15,7 @@ * along with this program. If not, see . */ +#include #include int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, @@ -211,6 +212,11 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, return -ENOMEM; } + if (depth && !round_robin) { + for_each_possible_cpu(i) + *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth; + } + sbq->wake_batch = sbq_calc_wake_batch(depth); atomic_set(&sbq->wake_index, 0); -- cgit v1.2.3 From b21d5b301794ae332eaa6e177d71fe8b77d3664c Mon Sep 17 00:00:00 2001 From: Matias Bjørling Date: Fri, 16 Sep 2016 14:25:06 +0200 Subject: blk-mq: register device instead of disk MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Enable devices without a gendisk instance to register itself with blk-mq and expose the associated multi-queue sysfs entries. Signed-off-by: Matias Bjørling Signed-off-by: Jens Axboe --- block/blk-mq-sysfs.c | 17 +++++++---------- block/blk-sysfs.c | 4 ++-- drivers/md/dm-rq.c | 2 +- include/linux/blk-mq.h | 4 ++-- 4 files changed, 12 insertions(+), 15 deletions(-) (limited to 'block') diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index 3c385b196bc7..01fb455d3377 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -393,9 +393,8 @@ static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx) return ret; } -static void __blk_mq_unregister_disk(struct gendisk *disk) +static void __blk_mq_unregister_dev(struct device *dev, struct request_queue *q) { - struct request_queue *q = disk->queue; struct blk_mq_hw_ctx *hctx; struct blk_mq_ctx *ctx; int i, j; @@ -413,15 +412,15 @@ static void __blk_mq_unregister_disk(struct gendisk *disk) kobject_del(&q->mq_kobj); kobject_put(&q->mq_kobj); - kobject_put(&disk_to_dev(disk)->kobj); + kobject_put(&dev->kobj); q->mq_sysfs_init_done = false; } -void blk_mq_unregister_disk(struct gendisk *disk) +void blk_mq_unregister_dev(struct device *dev, struct request_queue *q) { blk_mq_disable_hotplug(); - __blk_mq_unregister_disk(disk); + __blk_mq_unregister_dev(dev, q); blk_mq_enable_hotplug(); } @@ -443,10 +442,8 @@ static void blk_mq_sysfs_init(struct request_queue *q) } } -int blk_mq_register_disk(struct gendisk *disk) +int blk_mq_register_dev(struct device *dev, struct request_queue *q) { - struct device *dev = disk_to_dev(disk); - struct request_queue *q = disk->queue; struct blk_mq_hw_ctx *hctx; int ret, i; @@ -467,7 +464,7 @@ int blk_mq_register_disk(struct gendisk *disk) } if (ret) - __blk_mq_unregister_disk(disk); + __blk_mq_unregister_dev(dev, q); else q->mq_sysfs_init_done = true; out: @@ -475,7 +472,7 @@ out: return ret; } -EXPORT_SYMBOL_GPL(blk_mq_register_disk); +EXPORT_SYMBOL_GPL(blk_mq_register_dev); void blk_mq_sysfs_unregister(struct request_queue *q) { diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index f87a7e747d36..9cc8d7c5439a 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -704,7 +704,7 @@ int blk_register_queue(struct gendisk *disk) kobject_uevent(&q->kobj, KOBJ_ADD); if (q->mq_ops) - blk_mq_register_disk(disk); + blk_mq_register_dev(dev, q); if (!q->request_fn) return 0; @@ -729,7 +729,7 @@ void blk_unregister_queue(struct gendisk *disk) return; if (q->mq_ops) - blk_mq_unregister_disk(disk); + blk_mq_unregister_dev(disk_to_dev(disk), q); if (q->request_fn) elv_unregister_queue(q); diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 1ca7463e8bb2..ee48230a2952 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -955,7 +955,7 @@ int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t) dm_init_md_queue(md); /* backfill 'mq' sysfs registration normally done in blk_register_queue */ - blk_mq_register_disk(md->disk); + blk_mq_register_dev(disk_to_dev(md->disk), q); return 0; diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 2575779cf13f..fbcfdf323243 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -175,8 +175,8 @@ enum { struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *); struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, struct request_queue *q); -int blk_mq_register_disk(struct gendisk *); -void blk_mq_unregister_disk(struct gendisk *); +int blk_mq_register_dev(struct device *, struct request_queue *); +void blk_mq_unregister_dev(struct device *, struct request_queue *); int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set); void blk_mq_free_tag_set(struct blk_mq_tag_set *set); -- cgit v1.2.3 From 491221f88d00651e449c9caf7415b6453c8a77b7 Mon Sep 17 00:00:00 2001 From: Guoqing Jiang Date: Thu, 22 Sep 2016 03:10:01 -0400 Subject: block: export bio_free_pages to other modules bio_free_pages is introduced in commit 1dfa0f68c040 ("block: add a helper to free bio bounce buffer pages"), we can reuse the func in other modules after it was imported. Cc: Christoph Hellwig Cc: Jens Axboe Cc: Mike Snitzer Cc: Shaohua Li Signed-off-by: Guoqing Jiang Acked-by: Kent Overstreet Signed-off-by: Jens Axboe --- block/bio.c | 3 ++- drivers/md/bcache/btree.c | 6 +----- drivers/md/bcache/debug.c | 6 ++---- drivers/md/bcache/movinggc.c | 5 +---- drivers/md/bcache/request.c | 9 ++------- drivers/md/bcache/writeback.c | 5 +---- drivers/md/dm-log-writes.c | 6 +----- drivers/md/raid1.c | 8 ++------ include/linux/bio.h | 1 + 9 files changed, 13 insertions(+), 36 deletions(-) (limited to 'block') diff --git a/block/bio.c b/block/bio.c index a6d279e1ea9e..db85c5753a76 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1068,7 +1068,7 @@ static int bio_copy_to_iter(struct bio *bio, struct iov_iter iter) return 0; } -static void bio_free_pages(struct bio *bio) +void bio_free_pages(struct bio *bio) { struct bio_vec *bvec; int i; @@ -1076,6 +1076,7 @@ static void bio_free_pages(struct bio *bio) bio_for_each_segment_all(bvec, bio, i) __free_page(bvec->bv_page); } +EXPORT_SYMBOL(bio_free_pages); /** * bio_uncopy_user - finish previously mapped bio diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 76f7534d1dd1..81d3db40cd7b 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -361,12 +361,8 @@ static void __btree_node_write_done(struct closure *cl) static void btree_node_write_done(struct closure *cl) { struct btree *b = container_of(cl, struct btree, io); - struct bio_vec *bv; - int n; - - bio_for_each_segment_all(bv, b->bio, n) - __free_page(bv->bv_page); + bio_free_pages(b->bio); __btree_node_write_done(cl); } diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c index c28df164701e..333a1e5f6ae6 100644 --- a/drivers/md/bcache/debug.c +++ b/drivers/md/bcache/debug.c @@ -107,9 +107,8 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio) { char name[BDEVNAME_SIZE]; struct bio *check; - struct bio_vec bv, *bv2; + struct bio_vec bv; struct bvec_iter iter; - int i; check = bio_clone(bio, GFP_NOIO); if (!check) @@ -136,8 +135,7 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio) kunmap_atomic(p1); } - bio_for_each_segment_all(bv2, check, i) - __free_page(bv2->bv_page); + bio_free_pages(check); out_put: bio_put(check); } diff --git a/drivers/md/bcache/movinggc.c b/drivers/md/bcache/movinggc.c index 1881319f2298..5c4bddecfaf0 100644 --- a/drivers/md/bcache/movinggc.c +++ b/drivers/md/bcache/movinggc.c @@ -44,11 +44,8 @@ static void write_moving_finish(struct closure *cl) { struct moving_io *io = container_of(cl, struct moving_io, cl); struct bio *bio = &io->bio.bio; - struct bio_vec *bv; - int i; - bio_for_each_segment_all(bv, bio, i) - __free_page(bv->bv_page); + bio_free_pages(bio); if (io->op.replace_collision) trace_bcache_gc_copy_collision(&io->w->key); diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c index 4b177fe11ebb..40ffe5e424b3 100644 --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -694,13 +694,8 @@ static void cached_dev_cache_miss_done(struct closure *cl) if (s->iop.replace_collision) bch_mark_cache_miss_collision(s->iop.c, s->d); - if (s->iop.bio) { - int i; - struct bio_vec *bv; - - bio_for_each_segment_all(bv, s->iop.bio, i) - __free_page(bv->bv_page); - } + if (s->iop.bio) + bio_free_pages(s->iop.bio); cached_dev_bio_complete(cl); } diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index d9fd2a62e5f6..e51644e503a5 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -128,11 +128,8 @@ static void write_dirty_finish(struct closure *cl) struct dirty_io *io = container_of(cl, struct dirty_io, cl); struct keybuf_key *w = io->bio.bi_private; struct cached_dev *dc = io->dc; - struct bio_vec *bv; - int i; - bio_for_each_segment_all(bv, &io->bio, i) - __free_page(bv->bv_page); + bio_free_pages(&io->bio); /* This is kind of a dumb way of signalling errors. */ if (KEY_DIRTY(&w->key)) { diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c index 4ab68033f9d1..b52404159ccf 100644 --- a/drivers/md/dm-log-writes.c +++ b/drivers/md/dm-log-writes.c @@ -149,8 +149,6 @@ static void put_io_block(struct log_writes_c *lc) static void log_end_io(struct bio *bio) { struct log_writes_c *lc = bio->bi_private; - struct bio_vec *bvec; - int i; if (bio->bi_error) { unsigned long flags; @@ -161,9 +159,7 @@ static void log_end_io(struct bio *bio) spin_unlock_irqrestore(&lc->blocks_lock, flags); } - bio_for_each_segment_all(bvec, bio, i) - __free_page(bvec->bv_page); - + bio_free_pages(bio); put_io_block(lc); bio_put(bio); } diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 21dc00eb1989..1961d827dbd1 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -145,12 +145,8 @@ static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data) return r1_bio; out_free_pages: - while (--j >= 0) { - struct bio_vec *bv; - - bio_for_each_segment_all(bv, r1_bio->bios[j], i) - __free_page(bv->bv_page); - } + while (--j >= 0) + bio_free_pages(r1_bio->bios[j]); out_free_bio: while (++j < pi->raid_disks) diff --git a/include/linux/bio.h b/include/linux/bio.h index e00721a2dce1..97cb48f03dc7 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -459,6 +459,7 @@ static inline void bio_flush_dcache_pages(struct bio *bi) extern void bio_copy_data(struct bio *dst, struct bio *src); extern int bio_alloc_pages(struct bio *bio, gfp_t gfp); +extern void bio_free_pages(struct bio *bio); extern struct bio *bio_copy_user_iov(struct request_queue *, struct rq_map_data *, -- cgit v1.2.3 From 841bac2c87fc21c3ecf3bc3354855921735aeec1 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 21 Sep 2016 10:08:43 -0600 Subject: blk-mq: get rid of manual run of queue with __blk_mq_run_hw_queue() Two cases: 1) blk_mq_alloc_request() needlessly re-runs the queue, after calling into the tag allocation without NOWAIT set. We don't need to do that. 2) blk_mq_map_request() should just use blk_mq_run_hw_queue() with the async flag set to false. Signed-off-by: Jens Axboe Reviewed-by: Christoph Hellwig --- block/blk-mq.c | 16 ++-------------- 1 file changed, 2 insertions(+), 14 deletions(-) (limited to 'block') diff --git a/block/blk-mq.c b/block/blk-mq.c index e0a69daddbd8..c29700010b5c 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -34,8 +34,6 @@ static DEFINE_MUTEX(all_q_mutex); static LIST_HEAD(all_q_list); -static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx); - /* * Check if any of the ctx's have pending work in this hardware queue */ @@ -228,19 +226,9 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, ctx = blk_mq_get_ctx(q); hctx = q->mq_ops->map_queue(q, ctx->cpu); blk_mq_set_alloc_data(&alloc_data, q, flags, ctx, hctx); - rq = __blk_mq_alloc_request(&alloc_data, rw, 0); - if (!rq && !(flags & BLK_MQ_REQ_NOWAIT)) { - __blk_mq_run_hw_queue(hctx); - blk_mq_put_ctx(ctx); - - ctx = blk_mq_get_ctx(q); - hctx = q->mq_ops->map_queue(q, ctx->cpu); - blk_mq_set_alloc_data(&alloc_data, q, flags, ctx, hctx); - rq = __blk_mq_alloc_request(&alloc_data, rw, 0); - ctx = alloc_data.ctx; - } blk_mq_put_ctx(ctx); + if (!rq) { blk_queue_exit(q); return ERR_PTR(-EWOULDBLOCK); @@ -1225,7 +1213,7 @@ static struct request *blk_mq_map_request(struct request_queue *q, blk_mq_set_alloc_data(&alloc_data, q, BLK_MQ_REQ_NOWAIT, ctx, hctx); rq = __blk_mq_alloc_request(&alloc_data, op, op_flags); if (unlikely(!rq)) { - __blk_mq_run_hw_queue(hctx); + blk_mq_run_hw_queue(hctx, false); blk_mq_put_ctx(ctx); trace_block_sleeprq(q, bio, op); -- cgit v1.2.3 From 63581af3f31e0dbea112b83f77c4fbb6a10e1406 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 22 Sep 2016 11:38:23 -0700 Subject: blk-mq: remove non-blocking pass in blk_mq_map_request bt_get already does a non-blocking pass as well as running the queue when scheduling internally, no need to duplicate it. Signed-off-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-mq.c | 14 +------------- 1 file changed, 1 insertion(+), 13 deletions(-) (limited to 'block') diff --git a/block/blk-mq.c b/block/blk-mq.c index c29700010b5c..80d483864247 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1210,20 +1210,8 @@ static struct request *blk_mq_map_request(struct request_queue *q, op_flags |= REQ_SYNC; trace_block_getrq(q, bio, op); - blk_mq_set_alloc_data(&alloc_data, q, BLK_MQ_REQ_NOWAIT, ctx, hctx); + blk_mq_set_alloc_data(&alloc_data, q, 0, ctx, hctx); rq = __blk_mq_alloc_request(&alloc_data, op, op_flags); - if (unlikely(!rq)) { - blk_mq_run_hw_queue(hctx, false); - blk_mq_put_ctx(ctx); - trace_block_sleeprq(q, bio, op); - - ctx = blk_mq_get_ctx(q); - hctx = q->mq_ops->map_queue(q, ctx->cpu); - blk_mq_set_alloc_data(&alloc_data, q, 0, ctx, hctx); - rq = __blk_mq_alloc_request(&alloc_data, op, op_flags); - ctx = alloc_data.ctx; - hctx = alloc_data.hctx; - } hctx->queued++; data->hctx = hctx; -- cgit v1.2.3 From 1b792f2f92784c00db2e6431496e437855d6f12a Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Wed, 21 Sep 2016 10:12:13 -0600 Subject: blk-mq: add flag for drivers wanting blocking ->queue_rq() If a driver sets BLK_MQ_F_BLOCKING, it is allowed to block in its ->queue_rq() handler. For that case, blk-mq ensures that we always calls it from a safe context. Signed-off-by: Jens Axboe Tested-by: Josef Bacik --- block/blk-mq.c | 2 +- include/linux/blk-mq.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) (limited to 'block') diff --git a/block/blk-mq.c b/block/blk-mq.c index 80d483864247..e9ebe9864cc4 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -908,7 +908,7 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async) !blk_mq_hw_queue_mapped(hctx))) return; - if (!async) { + if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) { int cpu = get_cpu(); if (cpumask_test_cpu(cpu, hctx->cpumask)) { __blk_mq_run_hw_queue(hctx); diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index fbcfdf323243..5daa0ef756dd 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -155,6 +155,7 @@ enum { BLK_MQ_F_TAG_SHARED = 1 << 1, BLK_MQ_F_SG_MERGE = 1 << 2, BLK_MQ_F_DEFER_ISSUE = 1 << 4, + BLK_MQ_F_BLOCKING = 1 << 5, BLK_MQ_F_ALLOC_POLICY_START_BIT = 8, BLK_MQ_F_ALLOC_POLICY_BITS = 1, -- cgit v1.2.3 From 3932a86b4b9d1f0b049d64d4591ce58ad18b44ec Mon Sep 17 00:00:00 2001 From: Glauber Costa Date: Thu, 22 Sep 2016 20:59:59 -0400 Subject: cfq: fix starvation of asynchronous writes While debugging timeouts happening in my application workload (ScyllaDB), I have observed calls to open() taking a long time, ranging everywhere from 2 seconds - the first ones that are enough to time out my application - to more than 30 seconds. The problem seems to happen because XFS may block on pending metadata updates under certain circumnstances, and that's confirmed with the following backtrace taken by the offcputime tool (iovisor/bcc): ffffffffb90c57b1 finish_task_switch ffffffffb97dffb5 schedule ffffffffb97e310c schedule_timeout ffffffffb97e1f12 __down ffffffffb90ea821 down ffffffffc046a9dc xfs_buf_lock ffffffffc046abfb _xfs_buf_find ffffffffc046ae4a xfs_buf_get_map ffffffffc046babd xfs_buf_read_map ffffffffc0499931 xfs_trans_read_buf_map ffffffffc044a561 xfs_da_read_buf ffffffffc0451390 xfs_dir3_leaf_read.constprop.16 ffffffffc0452b90 xfs_dir2_leaf_lookup_int ffffffffc0452e0f xfs_dir2_leaf_lookup ffffffffc044d9d3 xfs_dir_lookup ffffffffc047d1d9 xfs_lookup ffffffffc0479e53 xfs_vn_lookup ffffffffb925347a path_openat ffffffffb9254a71 do_filp_open ffffffffb9242a94 do_sys_open ffffffffb9242b9e sys_open ffffffffb97e42b2 entry_SYSCALL_64_fastpath 00007fb0698162ed [unknown] Inspecting my run with blktrace, I can see that the xfsaild kthread exhibit very high "Dispatch wait" times, on the dozens of seconds range and consistent with the open() times I have saw in that run. Still from the blktrace output, we can after searching a bit, identify the request that wasn't dispatched: 8,0 11 152 81.092472813 804 A WM 141698288 + 8 <- (8,1) 141696240 8,0 11 153 81.092472889 804 Q WM 141698288 + 8 [xfsaild/sda1] 8,0 11 154 81.092473207 804 G WM 141698288 + 8 [xfsaild/sda1] 8,0 11 206 81.092496118 804 I WM 141698288 + 8 ( 22911) [xfsaild/sda1] <==== 'I' means Inserted (into the IO scheduler) ===================================> 8,0 0 289372 96.718761435 0 D WM 141698288 + 8 (15626265317) [swapper/0] <==== Only 15s later the CFQ scheduler dispatches the request ======================> As we can see above, in this particular example CFQ took 15 seconds to dispatch this request. Going back to the full trace, we can see that the xfsaild queue had plenty of opportunity to run, and it was selected as the active queue many times. It would just always be preempted by something else (example): 8,0 1 0 81.117912979 0 m N cfq1618SN / insert_request 8,0 1 0 81.117913419 0 m N cfq1618SN / add_to_rr 8,0 1 0 81.117914044 0 m N cfq1618SN / preempt 8,0 1 0 81.117914398 0 m N cfq767A / slice expired t=1 8,0 1 0 81.117914755 0 m N cfq767A / resid=40 8,0 1 0 81.117915340 0 m N / served: vt=1948520448 min_vt=1948520448 8,0 1 0 81.117915858 0 m N cfq767A / sl_used=1 disp=0 charge=0 iops=1 sect=0 where cfq767 is the xfsaild queue and cfq1618 corresponds to one of the ScyllaDB IO dispatchers. The requests preempting the xfsaild queue are synchronous requests. That's a characteristic of ScyllaDB workloads, as we only ever issue O_DIRECT requests. While it can be argued that preempting ASYNC requests in favor of SYNC is part of the CFQ logic, I don't believe that doing so for 15+ seconds is anyone's goal. Moreover, unless I am misunderstanding something, that breaks the expectation set by the "fifo_expire_async" tunable, which in my system is set to the default. Looking at the code, it seems to me that the issue is that after we make an async queue active, there is no guarantee that it will execute any request. When the queue itself tests if it cfq_may_dispatch() it can bail if it sees SYNC requests in flight. An incoming request from another queue can also preempt it in such situation before we have the chance to execute anything (as seen in the trace above). This patch sets the must_dispatch flag if we notice that we have requests that are already fifo_expired. This flag is always cleared after cfq_dispatch_request() returns from cfq_dispatch_requests(), so it won't pin the queue for subsequent requests (unless they are themselves expired) Care is taken during preempt to still allow rt requests to preempt us regardless. Testing my workload with this patch applied produces much better results. From the application side I see no timeouts, and the open() latency histogram generated by systemtap looks much better, with the worst outlier at 131ms: Latency histogram of xfs_buf_lock acquisition (microseconds): value |-------------------------------------------------- count 0 | 11 1 |@@@@ 161 2 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 1966 4 |@ 54 8 | 36 16 | 7 32 | 0 64 | 0 ~ 1024 | 0 2048 | 0 4096 | 1 8192 | 1 16384 | 2 32768 | 0 65536 | 0 131072 | 1 262144 | 0 524288 | 0 Signed-off-by: Glauber Costa CC: Jens Axboe CC: linux-block@vger.kernel.org CC: linux-kernel@vger.kernel.org Signed-off-by: Glauber Costa Signed-off-by: Jens Axboe --- block/cfq-iosched.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'block') diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index cc2f6dbd4303..5e24d880306c 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -3042,7 +3042,6 @@ static struct request *cfq_check_fifo(struct cfq_queue *cfqq) if (ktime_get_ns() < rq->fifo_time) rq = NULL; - cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq); return rq; } @@ -3420,6 +3419,9 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) { unsigned int max_dispatch; + if (cfq_cfqq_must_dispatch(cfqq)) + return true; + /* * Drain async requests before we start sync IO */ @@ -3511,15 +3513,20 @@ static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq) BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list)); + rq = cfq_check_fifo(cfqq); + if (rq) + cfq_mark_cfqq_must_dispatch(cfqq); + if (!cfq_may_dispatch(cfqd, cfqq)) return false; /* * follow expired path, else get first next available */ - rq = cfq_check_fifo(cfqq); if (!rq) rq = cfqq->next_rq; + else + cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq); /* * insert request into driver dispatch list @@ -3989,7 +3996,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq, * if the new request is sync, but the currently running queue is * not, let the sync request have priority. */ - if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq)) + if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) return true; /* -- cgit v1.2.3