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 <bvanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Damien Le Moal <damien.lemoal@xxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
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
