From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , Mike Snitzer , dm-devel@redhat.com Cc: Bart Van Assche , Laurence Oberman , Paolo Valente , Oleksandr Natalenko , Tom Nguyen , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, Omar Sandoval , Ming Lei Subject: [PATCH V5 2/7] blk-mq-sched: fix scheduler bad performance Date: Sat, 30 Sep 2017 18:27:15 +0800 Message-Id: <20170930102720.30219-3-ming.lei@redhat.com> In-Reply-To: <20170930102720.30219-1-ming.lei@redhat.com> References: <20170930102720.30219-1-ming.lei@redhat.com> Sender: linux-scsi-owner@vger.kernel.org List-ID: When hw queue is busy, we shouldn't take requests from scheduler queue any more, otherwise it is difficult to do IO merge. This patch fixes the awful IO performance on some SCSI devices(lpfc, qla2xxx, ...) when mq-deadline/kyber is used by not taking requests if hw queue is busy. Tested-by: Oleksandr Natalenko Tested-by: Tom Nguyen Tested-by: Paolo Valente Reviewed-by: Bart Van Assche Signed-off-by: Ming Lei --- block/blk-mq-sched.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 4ab69435708c..eca011fdfa0e 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -94,7 +94,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) struct request_queue *q = hctx->queue; struct elevator_queue *e = q->elevator; const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request; - bool did_work = false; + bool do_sched_dispatch = true; LIST_HEAD(rq_list); /* RCU or SRCU read lock is needed before checking quiesced flag */ @@ -125,18 +125,18 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) */ if (!list_empty(&rq_list)) { blk_mq_sched_mark_restart_hctx(hctx); - did_work = blk_mq_dispatch_rq_list(q, &rq_list); + do_sched_dispatch = blk_mq_dispatch_rq_list(q, &rq_list); } else if (!has_sched_dispatch) { blk_mq_flush_busy_ctxs(hctx, &rq_list); blk_mq_dispatch_rq_list(q, &rq_list); } /* - * We want to dispatch from the scheduler if we had no work left - * on the dispatch list, OR if we did have work but weren't able - * to make progress. + * 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 (!did_work && has_sched_dispatch) { + if (do_sched_dispatch && has_sched_dispatch) { do { struct request *rq; -- 2.9.5