From 65a558f66c308251e256317957b75d1e643c33c3 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 21 Jul 2023 10:27:30 -0700 Subject: block: Improve performance for BLK_MQ_F_BLOCKING drivers blk_mq_run_queue() runs the queue asynchronously if BLK_MQ_F_BLOCKING has been set. This is suboptimal since running the queue asynchronously is slower than running the queue synchronously. This patch modifies blk_mq_run_queue() as follows if BLK_MQ_F_BLOCKING has been set: - Run the queue synchronously if it is allowed to sleep. - Run the queue asynchronously if it is not allowed to sleep. Additionally, blk_mq_run_hw_queue(hctx, false) calls are modified into blk_mq_run_hw_queue(hctx, hctx->flags & BLK_MQ_F_BLOCKING) if the caller may be invoked from atomic context. The following caller chains have been reviewed: blk_mq_run_hw_queue(hctx, false) blk_mq_get_tag() /* may sleep, hence the functions it calls may also sleep */ blk_execute_rq() /* may sleep */ blk_mq_run_hw_queues(q, async=false) blk_freeze_queue_start() /* may sleep */ blk_mq_requeue_work() /* may sleep */ scsi_kick_queue() scsi_requeue_run_queue() /* may sleep */ scsi_run_host_queues() scsi_ioctl_reset() /* may sleep */ blk_mq_insert_requests(hctx, ctx, list, run_queue_async=false) blk_mq_dispatch_plug_list(plug, from_sched=false) blk_mq_flush_plug_list(plug, from_schedule=false) __blk_flush_plug(plug, from_schedule=false) blk_add_rq_to_plug() blk_mq_submit_bio() /* may sleep if REQ_NOWAIT has not been set */ blk_mq_plug_issue_direct() blk_mq_flush_plug_list() /* see above */ blk_mq_dispatch_plug_list(plug, from_sched=false) blk_mq_flush_plug_list() /* see above */ blk_mq_try_issue_directly() blk_mq_submit_bio() /* may sleep if REQ_NOWAIT has not been set */ blk_mq_try_issue_list_directly(hctx, list) blk_mq_insert_requests() /* see above */ Cc: Christoph Hellwig Cc: Ming Lei Signed-off-by: Bart Van Assche Link: https://lore.kernel.org/r/20230721172731.955724-4-bvanassche@acm.org Signed-off-by: Jens Axboe --- block/blk-mq.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) (limited to 'block/blk-mq.c') diff --git a/block/blk-mq.c b/block/blk-mq.c index d98654869615..687ec3f4f10d 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1323,7 +1323,7 @@ void blk_execute_rq_nowait(struct request *rq, bool at_head) } blk_mq_insert_request(rq, at_head ? BLK_MQ_INSERT_AT_HEAD : 0); - blk_mq_run_hw_queue(hctx, false); + blk_mq_run_hw_queue(hctx, hctx->flags & BLK_MQ_F_BLOCKING); } EXPORT_SYMBOL_GPL(blk_execute_rq_nowait); @@ -2222,6 +2222,8 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async) */ WARN_ON_ONCE(!async && in_interrupt()); + might_sleep_if(!async && hctx->flags & BLK_MQ_F_BLOCKING); + /* * When queue is quiesced, we may be switching io scheduler, or * updating nr_hw_queues, or other things, and we can't run queue @@ -2237,8 +2239,7 @@ void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async) if (!need_run) return; - if (async || (hctx->flags & BLK_MQ_F_BLOCKING) || - !cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask)) { + if (async || !cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask)) { blk_mq_delay_run_hw_queue(hctx, 0); return; } @@ -2373,7 +2374,7 @@ void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx) { clear_bit(BLK_MQ_S_STOPPED, &hctx->state); - blk_mq_run_hw_queue(hctx, false); + blk_mq_run_hw_queue(hctx, hctx->flags & BLK_MQ_F_BLOCKING); } EXPORT_SYMBOL(blk_mq_start_hw_queue); @@ -2403,7 +2404,8 @@ void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async) unsigned long i; queue_for_each_hw_ctx(q, hctx, i) - blk_mq_start_stopped_hw_queue(hctx, async); + blk_mq_start_stopped_hw_queue(hctx, async || + (hctx->flags & BLK_MQ_F_BLOCKING)); } EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues); @@ -2461,6 +2463,8 @@ static void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, list_for_each_entry(rq, list, queuelist) { BUG_ON(rq->mq_ctx != ctx); trace_block_rq_insert(rq); + if (rq->cmd_flags & REQ_NOWAIT) + run_queue_async = true; } spin_lock(&ctx->lock); @@ -2621,7 +2625,7 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx, if ((rq->rq_flags & RQF_USE_SCHED) || !blk_mq_get_budget_and_tag(rq)) { blk_mq_insert_request(rq, 0); - blk_mq_run_hw_queue(hctx, false); + blk_mq_run_hw_queue(hctx, rq->cmd_flags & REQ_NOWAIT); return; } -- cgit