dm bufio: when done scanning return from __scan immediately
authorMikulas Patocka <mpatocka@redhat.com>
Wed, 1 Oct 2014 17:29:48 +0000 (13:29 -0400)
committerMike Snitzer <snitzer@redhat.com>
Mon, 6 Oct 2014 00:03:37 +0000 (20:03 -0400)
commit0e825862f3c04cee40e25f55680333728a4ffa9b
treea036fac4e4bee64b32f71924b31acaf000184787
parenteb76faf53b1ff7a77ce3f78cc98ad392ac70c2a0
dm bufio: when done scanning return from __scan immediately

When __scan frees the required number of buffer entries that the
shrinker requested (nr_to_scan becomes zero) it must return.  Before
this fix the __scan code exited only the inner loop and continued in the
outer loop -- which could result in reduced performance due to extra
buffers being freed (e.g. unnecessarily evicted thinp metadata needing
to be synchronously re-read into bufio's cache).

Also, move dm_bufio_cond_resched to __scan's inner loop, so that
iterating the bufio client's lru lists doesn't result in scheduling
latency.

Reported-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.2+
drivers/md/dm-bufio.c