| From 0e825862f3c04cee40e25f55680333728a4ffa9b Mon Sep 17 00:00:00 2001 |
| From: Mikulas Patocka <mpatocka@redhat.com> |
| Date: Wed, 1 Oct 2014 13:29:48 -0400 |
| Subject: dm bufio: when done scanning return from __scan immediately |
| |
| From: Mikulas Patocka <mpatocka@redhat.com> |
| |
| commit 0e825862f3c04cee40e25f55680333728a4ffa9b upstream. |
| |
| 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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/md/dm-bufio.c | 4 ++-- |
| 1 file changed, 2 insertions(+), 2 deletions(-) |
| |
| --- a/drivers/md/dm-bufio.c |
| +++ b/drivers/md/dm-bufio.c |
| @@ -1473,9 +1473,9 @@ static long __scan(struct dm_bufio_clien |
| list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) { |
| freed += __cleanup_old_buffer(b, gfp_mask, 0); |
| if (!--nr_to_scan) |
| - break; |
| + return freed; |
| + dm_bufio_cond_resched(); |
| } |
| - dm_bufio_cond_resched(); |
| } |
| return freed; |
| } |
