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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
commit | 2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch) | |
tree | 848558de17fb3008cdf4d861b01ac7781903ce39 /block/blk-mq-sched.c | |
parent | Initial commit. (diff) | |
download | linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip |
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'block/blk-mq-sched.c')
-rw-r--r-- | block/blk-mq-sched.c | 673 |
1 files changed, 673 insertions, 0 deletions
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c new file mode 100644 index 000000000..91fb5d146 --- /dev/null +++ b/block/blk-mq-sched.c @@ -0,0 +1,673 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * blk-mq scheduling framework + * + * Copyright (C) 2016 Jens Axboe + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/blk-mq.h> +#include <linux/list_sort.h> + +#include <trace/events/block.h> + +#include "blk.h" +#include "blk-mq.h" +#include "blk-mq-debugfs.h" +#include "blk-mq-sched.h" +#include "blk-mq-tag.h" +#include "blk-wbt.h" + +/* + * Mark a hardware queue as needing a restart. + */ +void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx) +{ + if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) + return; + + set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); +} +EXPORT_SYMBOL_GPL(blk_mq_sched_mark_restart_hctx); + +void __blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) +{ + clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); + + /* + * Order clearing SCHED_RESTART and list_empty_careful(&hctx->dispatch) + * in blk_mq_run_hw_queue(). Its pair is the barrier in + * blk_mq_dispatch_rq_list(). So dispatch code won't see SCHED_RESTART, + * meantime new request added to hctx->dispatch is missed to check in + * blk_mq_run_hw_queue(). + */ + smp_mb(); + + blk_mq_run_hw_queue(hctx, true); +} + +static int sched_rq_cmp(void *priv, const struct list_head *a, + const struct list_head *b) +{ + struct request *rqa = container_of(a, struct request, queuelist); + struct request *rqb = container_of(b, struct request, queuelist); + + return rqa->mq_hctx > rqb->mq_hctx; +} + +static bool blk_mq_dispatch_hctx_list(struct list_head *rq_list) +{ + struct blk_mq_hw_ctx *hctx = + list_first_entry(rq_list, struct request, queuelist)->mq_hctx; + struct request *rq; + LIST_HEAD(hctx_list); + unsigned int count = 0; + + list_for_each_entry(rq, rq_list, queuelist) { + if (rq->mq_hctx != hctx) { + list_cut_before(&hctx_list, rq_list, &rq->queuelist); + goto dispatch; + } + count++; + } + list_splice_tail_init(rq_list, &hctx_list); + +dispatch: + return blk_mq_dispatch_rq_list(hctx, &hctx_list, count); +} + +#define BLK_MQ_BUDGET_DELAY 3 /* ms units */ + +/* + * Only SCSI implements .get_budget and .put_budget, and SCSI restarts + * its queue by itself in its completion handler, so we don't need to + * restart queue if .get_budget() fails to get the budget. + * + * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to + * be run again. This is necessary to avoid starving flushes. + */ +static int __blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + struct elevator_queue *e = q->elevator; + bool multi_hctxs = false, run_queue = false; + bool dispatched = false, busy = false; + unsigned int max_dispatch; + LIST_HEAD(rq_list); + int count = 0; + + if (hctx->dispatch_busy) + max_dispatch = 1; + else + max_dispatch = hctx->queue->nr_requests; + + do { + struct request *rq; + int budget_token; + + if (e->type->ops.has_work && !e->type->ops.has_work(hctx)) + break; + + if (!list_empty_careful(&hctx->dispatch)) { + busy = true; + break; + } + + budget_token = blk_mq_get_dispatch_budget(q); + if (budget_token < 0) + break; + + rq = e->type->ops.dispatch_request(hctx); + if (!rq) { + blk_mq_put_dispatch_budget(q, budget_token); + /* + * We're releasing without dispatching. Holding the + * budget could have blocked any "hctx"s with the + * same queue and if we didn't dispatch then there's + * no guarantee anyone will kick the queue. Kick it + * ourselves. + */ + run_queue = true; + break; + } + + blk_mq_set_rq_budget_token(rq, budget_token); + + /* + * Now this rq owns the budget which has to be released + * if this rq won't be queued to driver via .queue_rq() + * in blk_mq_dispatch_rq_list(). + */ + list_add_tail(&rq->queuelist, &rq_list); + count++; + if (rq->mq_hctx != hctx) + multi_hctxs = true; + + /* + * If we cannot get tag for the request, stop dequeueing + * requests from the IO scheduler. We are unlikely to be able + * to submit them anyway and it creates false impression for + * scheduling heuristics that the device can take more IO. + */ + if (!blk_mq_get_driver_tag(rq)) + break; + } while (count < max_dispatch); + + if (!count) { + if (run_queue) + blk_mq_delay_run_hw_queues(q, BLK_MQ_BUDGET_DELAY); + } else if (multi_hctxs) { + /* + * Requests from different hctx may be dequeued from some + * schedulers, such as bfq and deadline. + * + * Sort the requests in the list according to their hctx, + * dispatch batching requests from same hctx at a time. + */ + list_sort(NULL, &rq_list, sched_rq_cmp); + do { + dispatched |= blk_mq_dispatch_hctx_list(&rq_list); + } while (!list_empty(&rq_list)); + } else { + dispatched = blk_mq_dispatch_rq_list(hctx, &rq_list, count); + } + + if (busy) + return -EAGAIN; + return !!dispatched; +} + +static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) +{ + unsigned long end = jiffies + HZ; + int ret; + + do { + ret = __blk_mq_do_dispatch_sched(hctx); + if (ret != 1) + break; + if (need_resched() || time_is_before_jiffies(end)) { + blk_mq_delay_run_hw_queue(hctx, 0); + break; + } + } while (1); + + return ret; +} + +static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, + struct blk_mq_ctx *ctx) +{ + unsigned short idx = ctx->index_hw[hctx->type]; + + if (++idx == hctx->nr_ctx) + idx = 0; + + return hctx->ctxs[idx]; +} + +/* + * Only SCSI implements .get_budget and .put_budget, and SCSI restarts + * its queue by itself in its completion handler, so we don't need to + * restart queue if .get_budget() fails to get the budget. + * + * Returns -EAGAIN if hctx->dispatch was found non-empty and run_work has to + * be run again. This is necessary to avoid starving flushes. + */ +static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + LIST_HEAD(rq_list); + struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from); + int ret = 0; + struct request *rq; + + do { + int budget_token; + + if (!list_empty_careful(&hctx->dispatch)) { + ret = -EAGAIN; + break; + } + + if (!sbitmap_any_bit_set(&hctx->ctx_map)) + break; + + budget_token = blk_mq_get_dispatch_budget(q); + if (budget_token < 0) + break; + + rq = blk_mq_dequeue_from_ctx(hctx, ctx); + if (!rq) { + blk_mq_put_dispatch_budget(q, budget_token); + /* + * We're releasing without dispatching. Holding the + * budget could have blocked any "hctx"s with the + * same queue and if we didn't dispatch then there's + * no guarantee anyone will kick the queue. Kick it + * ourselves. + */ + blk_mq_delay_run_hw_queues(q, BLK_MQ_BUDGET_DELAY); + break; + } + + blk_mq_set_rq_budget_token(rq, budget_token); + + /* + * Now this rq owns the budget which has to be released + * if this rq won't be queued to driver via .queue_rq() + * in blk_mq_dispatch_rq_list(). + */ + list_add(&rq->queuelist, &rq_list); + + /* round robin for fair dispatch */ + ctx = blk_mq_next_ctx(hctx, rq->mq_ctx); + + } while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, 1)); + + WRITE_ONCE(hctx->dispatch_from, ctx); + return ret; +} + +static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + const bool has_sched = q->elevator; + int ret = 0; + LIST_HEAD(rq_list); + + /* + * If we have previous entries on our dispatch list, grab them first for + * more fair dispatch. + */ + if (!list_empty_careful(&hctx->dispatch)) { + spin_lock(&hctx->lock); + if (!list_empty(&hctx->dispatch)) + list_splice_init(&hctx->dispatch, &rq_list); + spin_unlock(&hctx->lock); + } + + /* + * Only ask the scheduler for requests, if we didn't have residual + * requests from the dispatch list. This is to avoid the case where + * we only ever dispatch a fraction of the requests available because + * of low device queue depth. Once we pull requests out of the IO + * scheduler, we can no longer merge or sort them. So it's best to + * leave them there for as long as we can. Mark the hw queue as + * needing a restart in that case. + * + * We want to dispatch from the scheduler if there was nothing + * on the dispatch list or we were able to dispatch from the + * dispatch list. + */ + if (!list_empty(&rq_list)) { + blk_mq_sched_mark_restart_hctx(hctx); + if (blk_mq_dispatch_rq_list(hctx, &rq_list, 0)) { + if (has_sched) + ret = blk_mq_do_dispatch_sched(hctx); + else + ret = blk_mq_do_dispatch_ctx(hctx); + } + } else if (has_sched) { + ret = blk_mq_do_dispatch_sched(hctx); + } else if (hctx->dispatch_busy) { + /* dequeue request one by one from sw queue if queue is busy */ + ret = blk_mq_do_dispatch_ctx(hctx); + } else { + blk_mq_flush_busy_ctxs(hctx, &rq_list); + blk_mq_dispatch_rq_list(hctx, &rq_list, 0); + } + + return ret; +} + +void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + + /* RCU or SRCU read lock is needed before checking quiesced flag */ + if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) + return; + + hctx->run++; + + /* + * A return of -EAGAIN is an indication that hctx->dispatch is not + * empty and we must run again in order to avoid starving flushes. + */ + if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN) { + if (__blk_mq_sched_dispatch_requests(hctx) == -EAGAIN) + blk_mq_run_hw_queue(hctx, true); + } +} + +bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio, + unsigned int nr_segs) +{ + struct elevator_queue *e = q->elevator; + struct blk_mq_ctx *ctx; + struct blk_mq_hw_ctx *hctx; + bool ret = false; + enum hctx_type type; + + if (e && e->type->ops.bio_merge) { + ret = e->type->ops.bio_merge(q, bio, nr_segs); + goto out_put; + } + + ctx = blk_mq_get_ctx(q); + hctx = blk_mq_map_queue(q, bio->bi_opf, ctx); + type = hctx->type; + if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE) || + list_empty_careful(&ctx->rq_lists[type])) + goto out_put; + + /* default per sw-queue merge */ + spin_lock(&ctx->lock); + /* + * Reverse check our software queue for entries that we could + * potentially merge with. Currently includes a hand-wavy stop + * count of 8, to not spend too much time checking for merges. + */ + if (blk_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) + ret = true; + + spin_unlock(&ctx->lock); +out_put: + return ret; +} + +bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq, + struct list_head *free) +{ + return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq, free); +} +EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge); + +static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, + struct request *rq) +{ + /* + * dispatch flush and passthrough rq directly + * + * passthrough request has to be added to hctx->dispatch directly. + * For some reason, device may be in one situation which can't + * handle FS request, so STS_RESOURCE is always returned and the + * FS request will be added to hctx->dispatch. However passthrough + * request may be required at that time for fixing the problem. If + * passthrough request is added to scheduler queue, there isn't any + * chance to dispatch it given we prioritize requests in hctx->dispatch. + */ + if ((rq->rq_flags & RQF_FLUSH_SEQ) || blk_rq_is_passthrough(rq)) + return true; + + return false; +} + +void blk_mq_sched_insert_request(struct request *rq, bool at_head, + bool run_queue, bool async) +{ + struct request_queue *q = rq->q; + struct elevator_queue *e = q->elevator; + struct blk_mq_ctx *ctx = rq->mq_ctx; + struct blk_mq_hw_ctx *hctx = rq->mq_hctx; + + WARN_ON(e && (rq->tag != BLK_MQ_NO_TAG)); + + if (blk_mq_sched_bypass_insert(hctx, rq)) { + /* + * Firstly normal IO request is inserted to scheduler queue or + * sw queue, meantime we add flush request to dispatch queue( + * hctx->dispatch) directly and there is at most one in-flight + * flush request for each hw queue, so it doesn't matter to add + * flush request to tail or front of the dispatch queue. + * + * Secondly in case of NCQ, flush request belongs to non-NCQ + * command, and queueing it will fail when there is any + * in-flight normal IO request(NCQ command). When adding flush + * rq to the front of hctx->dispatch, it is easier to introduce + * extra time to flush rq's latency because of S_SCHED_RESTART + * compared with adding to the tail of dispatch queue, then + * chance of flush merge is increased, and less flush requests + * will be issued to controller. It is observed that ~10% time + * is saved in blktests block/004 on disk attached to AHCI/NCQ + * drive when adding flush rq to the front of hctx->dispatch. + * + * Simply queue flush rq to the front of hctx->dispatch so that + * intensive flush workloads can benefit in case of NCQ HW. + */ + at_head = (rq->rq_flags & RQF_FLUSH_SEQ) ? true : at_head; + blk_mq_request_bypass_insert(rq, at_head, false); + goto run; + } + + if (e) { + LIST_HEAD(list); + + list_add(&rq->queuelist, &list); + e->type->ops.insert_requests(hctx, &list, at_head); + } else { + spin_lock(&ctx->lock); + __blk_mq_insert_request(hctx, rq, at_head); + spin_unlock(&ctx->lock); + } + +run: + if (run_queue) + blk_mq_run_hw_queue(hctx, async); +} + +void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx, + struct blk_mq_ctx *ctx, + struct list_head *list, bool run_queue_async) +{ + struct elevator_queue *e; + struct request_queue *q = hctx->queue; + + /* + * blk_mq_sched_insert_requests() is called from flush plug + * context only, and hold one usage counter to prevent queue + * from being released. + */ + percpu_ref_get(&q->q_usage_counter); + + e = hctx->queue->elevator; + if (e) { + e->type->ops.insert_requests(hctx, list, false); + } else { + /* + * try to issue requests directly if the hw queue isn't + * busy in case of 'none' scheduler, and this way may save + * us one extra enqueue & dequeue to sw queue. + */ + if (!hctx->dispatch_busy && !run_queue_async) { + blk_mq_run_dispatch_ops(hctx->queue, + blk_mq_try_issue_list_directly(hctx, list)); + if (list_empty(list)) + goto out; + } + blk_mq_insert_requests(hctx, ctx, list); + } + + blk_mq_run_hw_queue(hctx, run_queue_async); + out: + percpu_ref_put(&q->q_usage_counter); +} + +static int blk_mq_sched_alloc_map_and_rqs(struct request_queue *q, + struct blk_mq_hw_ctx *hctx, + unsigned int hctx_idx) +{ + if (blk_mq_is_shared_tags(q->tag_set->flags)) { + hctx->sched_tags = q->sched_shared_tags; + return 0; + } + + hctx->sched_tags = blk_mq_alloc_map_and_rqs(q->tag_set, hctx_idx, + q->nr_requests); + + if (!hctx->sched_tags) + return -ENOMEM; + return 0; +} + +static void blk_mq_exit_sched_shared_tags(struct request_queue *queue) +{ + blk_mq_free_rq_map(queue->sched_shared_tags); + queue->sched_shared_tags = NULL; +} + +/* called in queue's release handler, tagset has gone away */ +static void blk_mq_sched_tags_teardown(struct request_queue *q, unsigned int flags) +{ + struct blk_mq_hw_ctx *hctx; + unsigned long i; + + queue_for_each_hw_ctx(q, hctx, i) { + if (hctx->sched_tags) { + if (!blk_mq_is_shared_tags(flags)) + blk_mq_free_rq_map(hctx->sched_tags); + hctx->sched_tags = NULL; + } + } + + if (blk_mq_is_shared_tags(flags)) + blk_mq_exit_sched_shared_tags(q); +} + +static int blk_mq_init_sched_shared_tags(struct request_queue *queue) +{ + struct blk_mq_tag_set *set = queue->tag_set; + + /* + * Set initial depth at max so that we don't need to reallocate for + * updating nr_requests. + */ + queue->sched_shared_tags = blk_mq_alloc_map_and_rqs(set, + BLK_MQ_NO_HCTX_IDX, + MAX_SCHED_RQ); + if (!queue->sched_shared_tags) + return -ENOMEM; + + blk_mq_tag_update_sched_shared_tags(queue); + + return 0; +} + +int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) +{ + unsigned int flags = q->tag_set->flags; + struct blk_mq_hw_ctx *hctx; + struct elevator_queue *eq; + unsigned long i; + int ret; + + if (!e) { + blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q); + q->elevator = NULL; + q->nr_requests = q->tag_set->queue_depth; + return 0; + } + + /* + * Default to double of smaller one between hw queue_depth and 128, + * since we don't split into sync/async like the old code did. + * Additionally, this is a per-hw queue depth. + */ + q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth, + BLKDEV_DEFAULT_RQ); + + if (blk_mq_is_shared_tags(flags)) { + ret = blk_mq_init_sched_shared_tags(q); + if (ret) + return ret; + } + + queue_for_each_hw_ctx(q, hctx, i) { + ret = blk_mq_sched_alloc_map_and_rqs(q, hctx, i); + if (ret) + goto err_free_map_and_rqs; + } + + ret = e->ops.init_sched(q, e); + if (ret) + goto err_free_map_and_rqs; + + mutex_lock(&q->debugfs_mutex); + blk_mq_debugfs_register_sched(q); + mutex_unlock(&q->debugfs_mutex); + + queue_for_each_hw_ctx(q, hctx, i) { + if (e->ops.init_hctx) { + ret = e->ops.init_hctx(hctx, i); + if (ret) { + eq = q->elevator; + blk_mq_sched_free_rqs(q); + blk_mq_exit_sched(q, eq); + kobject_put(&eq->kobj); + return ret; + } + } + mutex_lock(&q->debugfs_mutex); + blk_mq_debugfs_register_sched_hctx(q, hctx); + mutex_unlock(&q->debugfs_mutex); + } + + return 0; + +err_free_map_and_rqs: + blk_mq_sched_free_rqs(q); + blk_mq_sched_tags_teardown(q, flags); + + q->elevator = NULL; + return ret; +} + +/* + * called in either blk_queue_cleanup or elevator_switch, tagset + * is required for freeing requests + */ +void blk_mq_sched_free_rqs(struct request_queue *q) +{ + struct blk_mq_hw_ctx *hctx; + unsigned long i; + + if (blk_mq_is_shared_tags(q->tag_set->flags)) { + blk_mq_free_rqs(q->tag_set, q->sched_shared_tags, + BLK_MQ_NO_HCTX_IDX); + } else { + queue_for_each_hw_ctx(q, hctx, i) { + if (hctx->sched_tags) + blk_mq_free_rqs(q->tag_set, + hctx->sched_tags, i); + } + } +} + +void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e) +{ + struct blk_mq_hw_ctx *hctx; + unsigned long i; + unsigned int flags = 0; + + queue_for_each_hw_ctx(q, hctx, i) { + mutex_lock(&q->debugfs_mutex); + blk_mq_debugfs_unregister_sched_hctx(hctx); + mutex_unlock(&q->debugfs_mutex); + + if (e->type->ops.exit_hctx && hctx->sched_data) { + e->type->ops.exit_hctx(hctx, i); + hctx->sched_data = NULL; + } + flags = hctx->flags; + } + + mutex_lock(&q->debugfs_mutex); + blk_mq_debugfs_unregister_sched(q); + mutex_unlock(&q->debugfs_mutex); + + if (e->type->ops.exit_sched) + e->type->ops.exit_sched(e); + blk_mq_sched_tags_teardown(q, flags); + q->elevator = NULL; +} |