diff options
| author | Chris Mason <chris.mason@fusionio.com> | 2012-07-23 15:25:05 -0400 |
|---|---|---|
| committer | Chris Mason <chris.mason@fusionio.com> | 2012-07-23 15:36:18 -0400 |
| commit | cbea5ac1ee03197354bd38caad3fcb798f185181 (patch) | |
| tree | 3d6b62c1fd163107ecb08d6489cf0bc159e6df12 | |
| parent | e39e64ac0cdeca3798a6bf186f873be20e2f57b4 (diff) | |
| download | linux-cbea5ac1ee03197354bd38caad3fcb798f185181.tar.bz2 | |
Btrfs: reduce calls to wake_up on uncontended locks
The btrfs locks were unconditionally calling wake_up as the
locks were released. This lead to extra thrashing on the waitqueue,
especially for locks that were dominated by readers.
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
| -rw-r--r-- | fs/btrfs/locking.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c index 272f911203ff..a44eff074805 100644 --- a/fs/btrfs/locking.c +++ b/fs/btrfs/locking.c @@ -78,13 +78,15 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw) write_lock(&eb->lock); WARN_ON(atomic_read(&eb->spinning_writers)); atomic_inc(&eb->spinning_writers); - if (atomic_dec_and_test(&eb->blocking_writers)) + if (atomic_dec_and_test(&eb->blocking_writers) && + waitqueue_active(&eb->write_lock_wq)) wake_up(&eb->write_lock_wq); } else if (rw == BTRFS_READ_LOCK_BLOCKING) { BUG_ON(atomic_read(&eb->blocking_readers) == 0); read_lock(&eb->lock); atomic_inc(&eb->spinning_readers); - if (atomic_dec_and_test(&eb->blocking_readers)) + if (atomic_dec_and_test(&eb->blocking_readers) && + waitqueue_active(&eb->read_lock_wq)) wake_up(&eb->read_lock_wq); } return; @@ -199,7 +201,8 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb) } btrfs_assert_tree_read_locked(eb); WARN_ON(atomic_read(&eb->blocking_readers) == 0); - if (atomic_dec_and_test(&eb->blocking_readers)) + if (atomic_dec_and_test(&eb->blocking_readers) && + waitqueue_active(&eb->read_lock_wq)) wake_up(&eb->read_lock_wq); atomic_dec(&eb->read_locks); } @@ -247,8 +250,9 @@ void btrfs_tree_unlock(struct extent_buffer *eb) if (blockers) { WARN_ON(atomic_read(&eb->spinning_writers)); atomic_dec(&eb->blocking_writers); - smp_wmb(); - wake_up(&eb->write_lock_wq); + smp_mb(); + if (waitqueue_active(&eb->write_lock_wq)) + wake_up(&eb->write_lock_wq); } else { WARN_ON(atomic_read(&eb->spinning_writers) != 1); atomic_dec(&eb->spinning_writers); |