From 79f720a751cad613620d0237e3b44f89f4a69181 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 10 Nov 2017 09:13:21 -0700 Subject: blk-mq: only run the hardware queue if IO is pending Currently we are inconsistent in when we decide to run the queue. Using blk_mq_run_hw_queues() we check if the hctx has pending IO before running it, but we don't do that from the individual queue run function, blk_mq_run_hw_queue(). This results in a lot of extra and pointless queue runs, potentially, on flush requests and (much worse) on tag starvation situations. This is observable just looking at top output, with lots of kworkers active. For the !async runs, it just adds to the CPU overhead of blk-mq. Move the has-pending check into the run function instead of having callers do it. Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-mq-sched.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) (limited to 'block/blk-mq-sched.c') diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 6f4bdb8209f7d..c117bd8fd1f61 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -81,12 +81,7 @@ static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx) } else clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); - if (blk_mq_hctx_has_pending(hctx)) { - blk_mq_run_hw_queue(hctx, true); - return true; - } - - return false; + return blk_mq_run_hw_queue(hctx, true); } /* -- cgit v1.2.3