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authorKent Overstreet <kmo@daterainc.com>2013-09-23 23:17:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-24 14:41:43 -0700
commitc2a4f3183a1248f615a695fbd8905da55ad11bba (patch)
tree51233866301869506c0728c812fe3668ae1e94ce /drivers/md/bcache/bcache.h
parent61cbd250f867f98bb4738000afc6002d6f2b14bd (diff)
bcache: Fix a writeback performance regression
Background writeback works by scanning the btree for dirty data and adding those keys into a fixed size buffer, then for each dirty key in the keybuf writing it to the backing device. When read_dirty() finishes and it's time to scan for more dirty data, we need to wait for the outstanding writeback IO to finish - they still take up slots in the keybuf (so that foreground writes can check for them to avoid races) - without that wait, we'll continually rescan when we'll be able to add at most a key or two to the keybuf, and that takes locks that starves foreground IO. Doh. Signed-off-by: Kent Overstreet <kmo@daterainc.com> Cc: linux-stable <stable@vger.kernel.org> # >= v3.10 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/md/bcache/bcache.h')
-rw-r--r--drivers/md/bcache/bcache.h7
1 files changed, 3 insertions, 4 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index b39f6f0b45f2..0f12382aa35d 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -498,7 +498,7 @@ struct cached_dev {
*/
atomic_t has_dirty;
- struct ratelimit writeback_rate;
+ struct bch_ratelimit writeback_rate;
struct delayed_work writeback_rate_update;
/*
@@ -507,10 +507,9 @@ struct cached_dev {
*/
sector_t last_read;
- /* Number of writeback bios in flight */
- atomic_t in_flight;
+ /* Limit number of writeback bios in flight */
+ struct semaphore in_flight;
struct closure_with_timer writeback;
- struct closure_waitlist writeback_wait;
struct keybuf writeback_keys;