From: Ming Lei <ming.lei@xxxxxxxxxx>
[ Upstream commit a12de1d42d74ef3c80e9fb9a2da94daaef747869 ]
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@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Javier González <javier@xxxxxxxxxxx>
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
block/blk-mq.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index a79b9ad1aba18..ed41cde93641c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1998,6 +1998,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
}
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)) {
/*
* We do limited plugging. If the bio can be merged, do that.
@@ -2021,8 +2023,8 @@ 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,
&cookie);
}
- } else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator &&
- !data.hctx->dispatch_busy)) {
+ } else if ((q->nr_hw_queues > 1 && is_sync) ||
+ !data.hctx->dispatch_busy) {
blk_mq_try_issue_directly(data.hctx, rq, &cookie);
} else {
blk_mq_sched_insert_request(rq, false, true, true);
--
2.20.1
