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blk-mq: honor IO scheduler for multiqueue devices 

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>
alistair/sunxi64-5.4-dsi
Ming Lei 2019-09-27 15:24:30 +08:00 committed by Jens Axboe
parent 8d6996630c
commit a12de1d42d
1 changed files with 4 additions and 2 deletions
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6
block/blk-mq.c
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@ -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);
} 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.
@ -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,
&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);