[PATCH 01/14] blk-mq-sched: fix scheduler bad performance
From: Ming Lei <hidden>
Date: 2017-07-31 16:51:44
Also in:
linux-scsi
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
When hw queue is busy, we shouldn't take requests from scheduler queue any more, otherwise IO merge will be difficult to do. 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. Signed-off-by: Ming Lei <redacted> --- block/blk-mq-sched.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 4ab69435708c..47a25333a136 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 can_go = true; LIST_HEAD(rq_list); /* RCU or SRCU read lock is needed before checking quiesced flag */
@@ -125,7 +125,7 @@ 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); + can_go = 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);
@@ -136,7 +136,7 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) * on the dispatch list, OR if we did have work but weren't able * to make progress. */ - if (!did_work && has_sched_dispatch) { + if (can_go && has_sched_dispatch) { do { struct request *rq;
--
2.9.4