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| author |   Chris Mason <chris.mason@oracle.com> | 2009-03-12 20:12:45 -0400 |
|---|---|---|
| committer | Chris Mason <chris.mason@oracle.com> | 2009-03-24 16:14:27 -0400 |
| commit | 66d7e85ea7c3628189d19b265495358f756cb463 (patch) | |
| tree | ffd9484c6e80f90bcf0c4da2f41dda57c8d6eac5 /fs/btrfs/locking.c | |
| parent | Btrfs: reduce stack in cow_file_range (diff) | |
| download | linux-dev-66d7e85ea7c3628189d19b265495358f756cb463.tar.xz linux-dev-66d7e85ea7c3628189d19b265495358f756cb463.zip | |
Btrfs: Check for a blocking lock before taking the spin
This reduces contention on the extent buffer spin locks by testing for a
blocking lock before trying to take the spinlock.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/locking.c')
| -rw-r--r-- | fs/btrfs/locking.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c index 47b0a88c12a2..6d8db2f5c38d 100644 --- a/fs/btrfs/locking.c +++ b/fs/btrfs/locking.c @@ -71,12 +71,13 @@ void btrfs_clear_lock_blocking(struct extent_buffer *eb) static int btrfs_spin_on_block(struct extent_buffer *eb) { int i; + for (i = 0; i < 512; i++) { - cpu_relax(); if (!test_bit(EXTENT_BUFFER_BLOCKING, &eb->bflags)) return 1; if (need_resched()) break; + cpu_relax(); } return 0; } @@ -102,6 +103,7 @@ int btrfs_try_spin_lock(struct extent_buffer *eb) /* spin for a bit on the BLOCKING flag */ for (i = 0; i < 2; i++) { + cpu_relax(); if (!btrfs_spin_on_block(eb)) break; @@ -148,6 +150,9 @@ int btrfs_tree_lock(struct extent_buffer *eb) DEFINE_WAIT(wait); wait.func = btrfs_wake_function; + if (!btrfs_spin_on_block(eb)) + goto sleep; + while(1) { spin_nested(eb); @@ -165,9 +170,10 @@ int btrfs_tree_lock(struct extent_buffer *eb) * spin for a bit, and if the blocking flag goes away, * loop around */ + cpu_relax(); if (btrfs_spin_on_block(eb)) continue; - +sleep: prepare_to_wait_exclusive(&eb->lock_wq, &wait, TASK_UNINTERRUPTIBLE); |