[dm-devel] [RFC PATCH 4/4] dm: delay running the queue slightly during request completion

[Mike Snitzer]

On really fast storage it can be beneficial to delay running the
request_queue to allow the elevator more opportunity to merge requests.

Otherwise, it has been observed that requests are being sent to
q->request_fn much quicker than is ideal on IOPS-bound backends.

Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
 drivers/md/dm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index fc92899..92091e0 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1034,7 +1034,7 @@ static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
 	 * queue lock again.
 	 */
 	if (run_queue)
-		blk_run_queue_async(md->queue);
+		blk_delay_queue(md->queue, HZ / 10);
 
 	/*
 	 * dm_put() must be at the end of this function. See the comment above
-- 
1.9.3 (Apple Git-50)