summaryrefslogtreecommitdiffstats
path: root/drivers/md/dm.c
diff options
context:
space:
mode:
authorMike Snitzer <snitzer@redhat.com>2015-02-24 11:03:22 -0500
committerMike Snitzer <snitzer@redhat.com>2015-04-15 12:10:12 -0400
commit9a0e609e3fd8a95c96629b9fbde6b8c5b9a1456a (patch)
treef16b43f956f54b0a1c214a8bba840b85217ed963 /drivers/md/dm.c
parentff36ab34583ae23250a4bf39805d69771e7e0131 (diff)
downloadlinux-9a0e609e3fd8a95c96629b9fbde6b8c5b9a1456a.tar.bz2
dm: only run the queue on completion if congested or no requests pending
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@redhat.com>
Diffstat (limited to 'drivers/md/dm.c')
-rw-r--r--drivers/md/dm.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 43e0d1a85a60..7924c00e0716 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1024,10 +1024,13 @@ static void end_clone_bio(struct bio *clone, int error)
*/
static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
{
+ int nr_requests_pending;
+
atomic_dec(&md->pending[rw]);
/* nudge anyone waiting on suspend queue */
- if (!md_in_flight(md))
+ nr_requests_pending = md_in_flight(md);
+ if (!nr_requests_pending)
wake_up(&md->wait);
/*
@@ -1036,8 +1039,11 @@ static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
* back into ->request_fn() could deadlock attempting to grab the
* queue lock again.
*/
- if (run_queue)
- blk_run_queue_async(md->queue);
+ if (run_queue) {
+ if (!nr_requests_pending ||
+ (nr_requests_pending >= md->queue->nr_congestion_on))
+ blk_run_queue_async(md->queue);
+ }
/*
* dm_put() must be at the end of this function. See the comment above