From 5815839b3ca16bb1d45939270871169f6803a121 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Mon, 25 Jun 2018 19:31:47 +0800 Subject: blk-mq: introduce new lock for protecting hctx->dispatch_wait Now hctx->lock is only acquired when adding hctx->dispatch_wait to one wait queue, but not held when removing it from the wait queue. IO hang can be observed easily if SCHED RESTART is disabled, that means now RESTART exits just for fixing the issue in blk_mq_mark_tag_wait(). This patch fixes the issue by introducing hctx->dispatch_wait_lock and holding it for removing hctx->dispatch_wait in blk_mq_dispatch_wake(), since we need to avoid acquiring hctx->lock in irq context. Fixes: eb619fdb2d4cb8b3d3419 ("blk-mq: fix issue with shared tag queue re-running") Cc: Christoph Hellwig Cc: Omar Sandoval Cc: Bart Van Assche Tested-by: Andrew Jones Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- include/linux/blk-mq.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/blk-mq.h') diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index e3147eb74222..ea690254dab7 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -39,6 +39,7 @@ struct blk_mq_hw_ctx { struct blk_mq_ctx **ctxs; unsigned int nr_ctx; + spinlock_t dispatch_wait_lock; wait_queue_entry_t dispatch_wait; atomic_t wait_index; -- cgit v1.2.1 From 6e768717304bdbe8d2897ca8298f6b58863fdc41 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 3 Jul 2018 09:03:16 -0600 Subject: blk-mq: dequeue request one by one from sw queue if hctx is busy It won't be efficient to dequeue request one by one from sw queue, but we have to do that when queue is busy for better merge performance. This patch takes the Exponential Weighted Moving Average(EWMA) to figure out if queue is busy, then only dequeue request one by one from sw queue when queue is busy. Fixes: b347689ffbca ("blk-mq-sched: improve dispatching from sw queue") Cc: Kashyap Desai Cc: Laurence Oberman Cc: Omar Sandoval Cc: Christoph Hellwig Cc: Bart Van Assche Cc: Hannes Reinecke Reported-by: Kashyap Desai Tested-by: Kashyap Desai Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- include/linux/blk-mq.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/linux/blk-mq.h') diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index ea690254dab7..d710e92874cc 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -35,9 +35,10 @@ struct blk_mq_hw_ctx { struct sbitmap ctx_map; struct blk_mq_ctx *dispatch_from; + unsigned int dispatch_busy; - struct blk_mq_ctx **ctxs; unsigned int nr_ctx; + struct blk_mq_ctx **ctxs; spinlock_t dispatch_wait_lock; wait_queue_entry_t dispatch_wait; -- cgit v1.2.1