Some HDD drive may expose multiple hw queue, such as MegraRaid, so still apply the normal plugging for such devices because sequential IO may benefit a lot from plug merging.
Cc: Bart Van Assche <[email protected]> Cc: Hannes Reinecke <[email protected]> Cc: Damien Le Moal <[email protected]> Cc: Dave Chinner <[email protected]> Signed-off-by: Ming Lei <[email protected]> --- block/blk-mq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index d7aed6518e62..969dfe02fa7c 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1983,10 +1983,14 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) /* bypass scheduler for flush rq */ blk_insert_flush(rq); blk_mq_run_hw_queue(data.hctx, true); - } else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs)) { + } else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs || + !blk_queue_nonrot(q))) { /* * Use plugging if we have a ->commit_rqs() hook as well, as * we know the driver uses bd->last in a smart fashion. + * + * Use normal plugging if this disk is slow HDD, as sequential + * IO may benefit a lot from plug merging. */ unsigned int request_count = plug->rq_count; struct request *last = NULL; -- 2.20.1
