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| author | Darrick J. Wong <djwong@kernel.org> | 2023-04-12 04:59:59 +0300 |
|---|---|---|
| committer | Darrick J. Wong <djwong@kernel.org> | 2023-04-12 04:59:59 +0300 |
| commit | 466c525d6d35e69115852c004f405f0711b8f91a (patch) | |
| tree | df8d1c75713f6c173c4193740864ec37a93aa4f3 /fs/xfs/Kconfig | |
| parent | 3f64c718d06eae168208faaadb522007e0048e7b (diff) | |
| download | linux-466c525d6d35e69115852c004f405f0711b8f91a.tar.xz | |
xfs: minimize overhead of drain wakeups by using jump labels
To reduce the runtime overhead even further when online fsck isn't
running, use a static branch key to decide if we call wake_up on the
drain. For compilers that support jump labels, the call to wake_up is
replaced by a nop sled when nobody is waiting for intents to drain.
From my initial microbenchmarking, every transition of the static key
between the on and off states takes about 22000ns to complete; this is
paid entirely by the xfs_scrub process. When the static key is off
(which it should be when fsck isn't running), the nop sled adds an
overhead of approximately 0.36ns to runtime code. The post-atomic
lockless waiter check adds about 0.03ns, which is basically free.
For the few compilers that don't support jump labels, runtime code pays
the cost of calling wake_up on an empty waitqueue, which was observed to
be about 30ns. However, most architectures that have sufficient memory
and CPU capacity to run XFS also support jump labels, so this is not
much of a worry.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Diffstat (limited to 'fs/xfs/Kconfig')
| -rw-r--r-- | fs/xfs/Kconfig | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig index ab24e683b440..05bc865142b8 100644 --- a/fs/xfs/Kconfig +++ b/fs/xfs/Kconfig @@ -95,6 +95,7 @@ config XFS_RT config XFS_DRAIN_INTENTS bool + select JUMP_LABEL if HAVE_ARCH_JUMP_LABEL config XFS_ONLINE_SCRUB bool "XFS online metadata check support" |