blk-mq: honor IO scheduler for multiqueue devices (a12de1d4) · Commits · 戴 / test

If a device is using multiple queues, the IO scheduler may be bypassed. This may hurt performance for some slow MQ devices, and it also breaks zoned devices which depend on mq-deadline for respecting the write order in one zone. Don't bypass io scheduler if we have one setup. This patch can double sequential write performance basically on MQ scsi_debug when mq-deadline is applied. Cc: Bart Van Assche <bvanassche@acm.org> Cc: Hannes Reinecke <hare@suse.com> Cc: Dave Chinner <dchinner@redhat.com> Reviewed-by:

Javier González <javier@javigon.com> Reviewed-by:

Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by:

Ming Lei <ming.lei@redhat.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-mq.c

+4 −2

Original line number	Original line	Diff line number	Diff line
	@@ -2012,6 +2012,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue q, struct bio bio)
	}		}

	blk_add_rq_to_plug(plug, rq);		blk_add_rq_to_plug(plug, rq);
			} else if (q->elevator) {
			blk_mq_sched_insert_request(rq, false, true, true);
	} else if (plug && !blk_queue_nomerges(q)) {		} else if (plug && !blk_queue_nomerges(q)) {
	/*		/*
	* We do limited plugging. If the bio can be merged, do that.		* We do limited plugging. If the bio can be merged, do that.
	@@ -2035,8 +2037,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue q, struct bio bio)
	blk_mq_try_issue_directly(data.hctx, same_queue_rq,		blk_mq_try_issue_directly(data.hctx, same_queue_rq,
	&cookie);		&cookie);
	}		}
	} else if ((q->nr_hw_queues > 1 && is_sync) \|\| (!q->elevator &&		} else if ((q->nr_hw_queues > 1 && is_sync) \|\|
	!data.hctx->dispatch_busy)) {		!data.hctx->dispatch_busy) {
	blk_mq_try_issue_directly(data.hctx, rq, &cookie);		blk_mq_try_issue_directly(data.hctx, rq, &cookie);
	} else {		} else {
	blk_mq_sched_insert_request(rq, false, true, true);		blk_mq_sched_insert_request(rq, false, true, true);

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