From 85dcb3c850a79751b2239f434a4b6b36a75a865e Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Sat, 14 Oct 2017 17:22:25 +0800 Subject: [PATCH] blk-mq-sched: dispatch from scheduler IFF progress is made in ->dispatch [ Upstream commit 5e3d02bbafad38975099b5848f5ebadedcf7bb7e ] When the hw queue is busy, we shouldn't take requests from the 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. Reviewed-by: Omar Sandoval Reviewed-by: Bart Van Assche Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- 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 4ab6943..eca011f 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; -- 2.7.4