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| author | Mike Snitzer <snitzer@redhat.com> | 2015-02-24 11:03:22 -0500 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-04-15 12:10:12 -0400 |
| commit | 9a0e609e3fd8a95c96629b9fbde6b8c5b9a1456a (patch) | |
| tree | f16b43f956f54b0a1c214a8bba840b85217ed963 /drivers/md/dm.c | |
| parent | ff36ab34583ae23250a4bf39805d69771e7e0131 (diff) | |
| download | lwn-9a0e609e3fd8a95c96629b9fbde6b8c5b9a1456a.tar.gz lwn-9a0e609e3fd8a95c96629b9fbde6b8c5b9a1456a.zip | |
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.c | 12 |
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 |