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block/blk-mq-sched.c
15.7 KB
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// SPDX-License-Identifier: GPL-2.0 |
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/* * blk-mq scheduling framework * * Copyright (C) 2016 Jens Axboe */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/blk-mq.h> #include <trace/events/block.h> #include "blk.h" #include "blk-mq.h" |
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#include "blk-mq-debugfs.h" |
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#include "blk-mq-sched.h" #include "blk-mq-tag.h" #include "blk-wbt.h" void blk_mq_sched_free_hctx_data(struct request_queue *q, void (*exit)(struct blk_mq_hw_ctx *)) { struct blk_mq_hw_ctx *hctx; int i; queue_for_each_hw_ctx(q, hctx, i) { if (exit && hctx->sched_data) exit(hctx); kfree(hctx->sched_data); hctx->sched_data = NULL; } } EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data); |
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void blk_mq_sched_assign_ioc(struct request *rq) |
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{ |
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struct request_queue *q = rq->q; |
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struct io_context *ioc; |
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struct io_cq *icq; |
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/* * May not have an IO context if it's a passthrough request */ ioc = current->io_context; if (!ioc) return; |
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spin_lock_irq(&q->queue_lock); |
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icq = ioc_lookup_icq(ioc, q); |
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spin_unlock_irq(&q->queue_lock); |
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if (!icq) { icq = ioc_create_icq(ioc, q, GFP_ATOMIC); if (!icq) return; } |
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get_io_context(icq->ioc); |
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rq->elv.icq = icq; |
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} |
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/* * Mark a hardware queue as needing a restart. For shared queues, maintain * a count of how many hardware queues are marked for restart. */ |
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void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx) |
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{ if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) return; |
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set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); |
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} |
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EXPORT_SYMBOL_GPL(blk_mq_sched_mark_restart_hctx); |
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|
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void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) |
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{ if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) |
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return; clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); |
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|
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blk_mq_run_hw_queue(hctx, true); |
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} |
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/* * 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() returns BLK_STS_NO_RESOURCE. */ static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) |
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{ struct request_queue *q = hctx->queue; struct elevator_queue *e = q->elevator; LIST_HEAD(rq_list); do { |
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struct request *rq; |
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|
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if (e->type->ops.has_work && !e->type->ops.has_work(hctx)) |
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break; |
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|
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if (!blk_mq_get_dispatch_budget(hctx)) |
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break; |
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|
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rq = e->type->ops.dispatch_request(hctx); |
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if (!rq) { blk_mq_put_dispatch_budget(hctx); break; |
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} /* * 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(). */ |
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list_add(&rq->queuelist, &rq_list); |
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} while (blk_mq_dispatch_rq_list(q, &rq_list, true)); |
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} |
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static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx) { |
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unsigned short idx = ctx->index_hw[hctx->type]; |
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if (++idx == hctx->nr_ctx) idx = 0; return hctx->ctxs[idx]; } |
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/* * 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() returns BLK_STS_NO_RESOURCE. */ static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) |
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{ struct request_queue *q = hctx->queue; LIST_HEAD(rq_list); struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from); do { struct request *rq; |
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if (!sbitmap_any_bit_set(&hctx->ctx_map)) break; |
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if (!blk_mq_get_dispatch_budget(hctx)) |
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break; |
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rq = blk_mq_dequeue_from_ctx(hctx, ctx); if (!rq) { blk_mq_put_dispatch_budget(hctx); break; |
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} /* * 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(q, &rq_list, true)); WRITE_ONCE(hctx->dispatch_from, ctx); |
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} |
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void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) |
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{ |
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struct request_queue *q = hctx->queue; struct elevator_queue *e = q->elevator; |
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const bool has_sched_dispatch = e && e->type->ops.dispatch_request; |
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LIST_HEAD(rq_list); |
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/* RCU or SRCU read lock is needed before checking quiesced flag */ if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) |
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return; |
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hctx->run++; /* * 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. |
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* * 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. |
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*/ |
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if (!list_empty(&rq_list)) { |
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blk_mq_sched_mark_restart_hctx(hctx); |
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if (blk_mq_dispatch_rq_list(q, &rq_list, false)) { if (has_sched_dispatch) |
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blk_mq_do_dispatch_sched(hctx); |
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else |
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blk_mq_do_dispatch_ctx(hctx); |
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} |
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} else if (has_sched_dispatch) { |
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blk_mq_do_dispatch_sched(hctx); |
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} else if (hctx->dispatch_busy) { /* dequeue request one by one from sw queue if queue is busy */ |
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blk_mq_do_dispatch_ctx(hctx); |
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} else { |
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blk_mq_flush_busy_ctxs(hctx, &rq_list); |
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blk_mq_dispatch_rq_list(q, &rq_list, false); |
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} |
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} |
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bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, |
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unsigned int nr_segs, struct request **merged_request) |
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{ struct request *rq; |
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|
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switch (elv_merge(q, &rq, bio)) { case ELEVATOR_BACK_MERGE: |
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if (!blk_mq_sched_allow_merge(q, rq, bio)) return false; |
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if (!bio_attempt_back_merge(rq, bio, nr_segs)) |
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return false; *merged_request = attempt_back_merge(q, rq); if (!*merged_request) elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); return true; case ELEVATOR_FRONT_MERGE: |
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if (!blk_mq_sched_allow_merge(q, rq, bio)) return false; |
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if (!bio_attempt_front_merge(rq, bio, nr_segs)) |
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return false; *merged_request = attempt_front_merge(q, rq); if (!*merged_request) elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); return true; |
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case ELEVATOR_DISCARD_MERGE: return bio_attempt_discard_merge(q, rq, bio); |
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default: return false; |
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} |
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} EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); |
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/* |
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* Iterate list of requests and see if we can merge this bio with any * of them. |
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*/ |
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bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list, |
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struct bio *bio, unsigned int nr_segs) |
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{ struct request *rq; int checked = 8; |
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list_for_each_entry_reverse(rq, list, queuelist) { |
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bool merged = false; if (!checked--) break; if (!blk_rq_merge_ok(rq, bio)) continue; switch (blk_try_merge(rq, bio)) { case ELEVATOR_BACK_MERGE: if (blk_mq_sched_allow_merge(q, rq, bio)) |
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merged = bio_attempt_back_merge(rq, bio, nr_segs); |
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break; case ELEVATOR_FRONT_MERGE: if (blk_mq_sched_allow_merge(q, rq, bio)) |
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merged = bio_attempt_front_merge(rq, bio, nr_segs); |
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break; case ELEVATOR_DISCARD_MERGE: merged = bio_attempt_discard_merge(q, rq, bio); break; default: continue; } |
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return merged; } return false; } |
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EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge); /* * 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. */ static bool blk_mq_attempt_merge(struct request_queue *q, |
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struct blk_mq_hw_ctx *hctx, |
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struct blk_mq_ctx *ctx, struct bio *bio, unsigned int nr_segs) |
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{ |
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enum hctx_type type = hctx->type; |
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lockdep_assert_held(&ctx->lock); |
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if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio, nr_segs)) { |
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ctx->rq_merged++; return true; } return false; } |
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|
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bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs) |
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{ struct elevator_queue *e = q->elevator; |
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struct blk_mq_ctx *ctx = blk_mq_get_ctx(q); |
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struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx); |
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bool ret = false; |
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enum hctx_type type; |
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|
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if (e && e->type->ops.bio_merge) |
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return e->type->ops.bio_merge(hctx, bio, nr_segs); |
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|
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type = hctx->type; |
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if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) && |
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!list_empty_careful(&ctx->rq_lists[type])) { |
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/* default per sw-queue merge */ spin_lock(&ctx->lock); |
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ret = blk_mq_attempt_merge(q, hctx, ctx, bio, nr_segs); |
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spin_unlock(&ctx->lock); } |
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return ret; |
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} bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq) { return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq); } EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge); void blk_mq_sched_request_inserted(struct request *rq) { trace_block_rq_insert(rq->q, rq); } EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted); |
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static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, |
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bool has_sched, |
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struct request *rq) |
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{ |
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/* * 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)) |
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return true; |
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|
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if (has_sched) |
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rq->rq_flags |= RQF_SORTED; |
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|
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return false; |
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} |
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|
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void blk_mq_sched_insert_request(struct request *rq, bool at_head, |
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bool run_queue, bool async) |
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{ struct request_queue *q = rq->q; struct elevator_queue *e = q->elevator; struct blk_mq_ctx *ctx = rq->mq_ctx; |
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struct blk_mq_hw_ctx *hctx = rq->mq_hctx; |
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|
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/* flush rq in flush machinery need to be dispatched directly */ if (!(rq->rq_flags & RQF_FLUSH_SEQ) && op_is_flush(rq->cmd_flags)) { |
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blk_insert_flush(rq); goto run; |
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} |
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WARN_ON(e && (rq->tag != -1)); |
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if (blk_mq_sched_bypass_insert(hctx, !!e, rq)) { |
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/* * 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; |
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blk_mq_request_bypass_insert(rq, at_head, false); |
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goto run; |
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} |
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|
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if (e && e->type->ops.insert_requests) { |
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LIST_HEAD(list); list_add(&rq->queuelist, &list); |
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e->type->ops.insert_requests(hctx, &list, at_head); |
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411 412 413 414 415 |
} else { spin_lock(&ctx->lock); __blk_mq_insert_request(hctx, rq, at_head); spin_unlock(&ctx->lock); } |
0cacba6cf blk-mq-sched: byp... |
416 |
run: |
bd6737f1a blk-mq-sched: add... |
417 418 419 |
if (run_queue) blk_mq_run_hw_queue(hctx, async); } |
67cae4c94 blk-mq: cleanup a... |
420 |
void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx, |
bd6737f1a blk-mq-sched: add... |
421 422 423 |
struct blk_mq_ctx *ctx, struct list_head *list, bool run_queue_async) { |
f9afca4d3 blk-mq: pass in r... |
424 |
struct elevator_queue *e; |
e87eb301b blk-mq: grab .q_u... |
425 426 427 428 429 430 431 432 |
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); |
bd6737f1a blk-mq-sched: add... |
433 |
|
f9afca4d3 blk-mq: pass in r... |
434 |
e = hctx->queue->elevator; |
f9cd4bfe9 block: get rid of... |
435 436 |
if (e && e->type->ops.insert_requests) e->type->ops.insert_requests(hctx, list, false); |
6ce3dd6ee blk-mq: issue dir... |
437 438 439 440 441 442 |
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. */ |
fd9c40f64 block: Revert v5.... |
443 |
if (!hctx->dispatch_busy && !e && !run_queue_async) { |
6ce3dd6ee blk-mq: issue dir... |
444 |
blk_mq_try_issue_list_directly(hctx, list); |
fd9c40f64 block: Revert v5.... |
445 |
if (list_empty(list)) |
e87eb301b blk-mq: grab .q_u... |
446 |
goto out; |
fd9c40f64 block: Revert v5.... |
447 448 |
} blk_mq_insert_requests(hctx, ctx, list); |
6ce3dd6ee blk-mq: issue dir... |
449 |
} |
bd6737f1a blk-mq-sched: add... |
450 451 |
blk_mq_run_hw_queue(hctx, run_queue_async); |
e87eb301b blk-mq: grab .q_u... |
452 453 |
out: percpu_ref_put(&q->q_usage_counter); |
bd6737f1a blk-mq-sched: add... |
454 |
} |
bd166ef18 blk-mq-sched: add... |
455 456 457 458 459 460 461 462 463 464 |
static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set, struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) { if (hctx->sched_tags) { blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx); blk_mq_free_rq_map(hctx->sched_tags); hctx->sched_tags = NULL; } } |
6917ff0b5 blk-mq-sched: ref... |
465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 |
static int blk_mq_sched_alloc_tags(struct request_queue *q, struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) { struct blk_mq_tag_set *set = q->tag_set; int ret; hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests, set->reserved_tags); if (!hctx->sched_tags) return -ENOMEM; ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests); if (ret) blk_mq_sched_free_tags(set, hctx, hctx_idx); return ret; } |
c3e221921 block: free sched... |
483 |
/* called in queue's release handler, tagset has gone away */ |
54d5329d4 blk-mq-sched: fix... |
484 |
static void blk_mq_sched_tags_teardown(struct request_queue *q) |
bd166ef18 blk-mq-sched: add... |
485 |
{ |
bd166ef18 blk-mq-sched: add... |
486 |
struct blk_mq_hw_ctx *hctx; |
6917ff0b5 blk-mq-sched: ref... |
487 |
int i; |
c3e221921 block: free sched... |
488 489 490 491 492 493 |
queue_for_each_hw_ctx(q, hctx, i) { if (hctx->sched_tags) { blk_mq_free_rq_map(hctx->sched_tags); hctx->sched_tags = NULL; } } |
6917ff0b5 blk-mq-sched: ref... |
494 495 496 497 498 |
} int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) { struct blk_mq_hw_ctx *hctx; |
ee056f981 blk-mq-sched: pro... |
499 |
struct elevator_queue *eq; |
6917ff0b5 blk-mq-sched: ref... |
500 501 502 503 504 |
unsigned int i; int ret; if (!e) { q->elevator = NULL; |
32a50fabb blk-mq: update nr... |
505 |
q->nr_requests = q->tag_set->queue_depth; |
6917ff0b5 blk-mq-sched: ref... |
506 507 |
return 0; } |
bd166ef18 blk-mq-sched: add... |
508 509 |
/* |
32825c45f blk-mq-sched: fix... |
510 511 512 |
* 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. |
bd166ef18 blk-mq-sched: add... |
513 |
*/ |
32825c45f blk-mq-sched: fix... |
514 515 |
q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth, BLKDEV_MAX_RQ); |
bd166ef18 blk-mq-sched: add... |
516 |
|
bd166ef18 blk-mq-sched: add... |
517 |
queue_for_each_hw_ctx(q, hctx, i) { |
6917ff0b5 blk-mq-sched: ref... |
518 |
ret = blk_mq_sched_alloc_tags(q, hctx, i); |
bd166ef18 blk-mq-sched: add... |
519 |
if (ret) |
6917ff0b5 blk-mq-sched: ref... |
520 |
goto err; |
bd166ef18 blk-mq-sched: add... |
521 |
} |
f9cd4bfe9 block: get rid of... |
522 |
ret = e->ops.init_sched(q, e); |
6917ff0b5 blk-mq-sched: ref... |
523 524 |
if (ret) goto err; |
bd166ef18 blk-mq-sched: add... |
525 |
|
d332ce091 blk-mq-debugfs: a... |
526 527 528 |
blk_mq_debugfs_register_sched(q); queue_for_each_hw_ctx(q, hctx, i) { |
f9cd4bfe9 block: get rid of... |
529 530 |
if (e->ops.init_hctx) { ret = e->ops.init_hctx(hctx, i); |
ee056f981 blk-mq-sched: pro... |
531 532 |
if (ret) { eq = q->elevator; |
c3e221921 block: free sched... |
533 |
blk_mq_sched_free_requests(q); |
ee056f981 blk-mq-sched: pro... |
534 535 536 537 538 |
blk_mq_exit_sched(q, eq); kobject_put(&eq->kobj); return ret; } } |
d332ce091 blk-mq-debugfs: a... |
539 |
blk_mq_debugfs_register_sched_hctx(q, hctx); |
ee056f981 blk-mq-sched: pro... |
540 |
} |
bd166ef18 blk-mq-sched: add... |
541 |
return 0; |
bd166ef18 blk-mq-sched: add... |
542 |
|
6917ff0b5 blk-mq-sched: ref... |
543 |
err: |
c3e221921 block: free sched... |
544 |
blk_mq_sched_free_requests(q); |
54d5329d4 blk-mq-sched: fix... |
545 546 |
blk_mq_sched_tags_teardown(q); q->elevator = NULL; |
6917ff0b5 blk-mq-sched: ref... |
547 |
return ret; |
bd166ef18 blk-mq-sched: add... |
548 |
} |
d34849913 blk-mq-sched: all... |
549 |
|
c3e221921 block: free sched... |
550 551 552 553 554 555 556 557 |
/* * called in either blk_queue_cleanup or elevator_switch, tagset * is required for freeing requests */ void blk_mq_sched_free_requests(struct request_queue *q) { struct blk_mq_hw_ctx *hctx; int i; |
c3e221921 block: free sched... |
558 559 560 561 562 |
queue_for_each_hw_ctx(q, hctx, i) { if (hctx->sched_tags) blk_mq_free_rqs(q->tag_set, hctx->sched_tags, i); } } |
54d5329d4 blk-mq-sched: fix... |
563 564 |
void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e) { |
ee056f981 blk-mq-sched: pro... |
565 566 |
struct blk_mq_hw_ctx *hctx; unsigned int i; |
d332ce091 blk-mq-debugfs: a... |
567 568 |
queue_for_each_hw_ctx(q, hctx, i) { blk_mq_debugfs_unregister_sched_hctx(hctx); |
f9cd4bfe9 block: get rid of... |
569 570 |
if (e->type->ops.exit_hctx && hctx->sched_data) { e->type->ops.exit_hctx(hctx, i); |
d332ce091 blk-mq-debugfs: a... |
571 |
hctx->sched_data = NULL; |
ee056f981 blk-mq-sched: pro... |
572 573 |
} } |
d332ce091 blk-mq-debugfs: a... |
574 |
blk_mq_debugfs_unregister_sched(q); |
f9cd4bfe9 block: get rid of... |
575 576 |
if (e->type->ops.exit_sched) e->type->ops.exit_sched(e); |
54d5329d4 blk-mq-sched: fix... |
577 578 579 |
blk_mq_sched_tags_teardown(q); q->elevator = NULL; } |