diff options
| author | Mateusz Guzik <mjguzik@gmail.com> | 2026-05-16 05:18:52 +0300 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2026-05-21 14:39:36 +0300 |
| commit | 7dc6acb3d56bc2c5d119c86abd8fe96034084fc8 (patch) | |
| tree | 3e58dea963d36e82e3e73961aa8ce46e53546d3a | |
| parent | 50d377ef12d9680ff8fd0923afc7edaf63995511 (diff) | |
| download | linux-7dc6acb3d56bc2c5d119c86abd8fe96034084fc8.tar.xz | |
fs/pipe: write to ->poll_usage only once
Both GNU and BSD makes share a "token pipe" between their instances, as
a result a -j $BIGNUM invocation results in multicore perf problems in
the poll handler.
Avoiding the store will reduce it a little bit. However, the crux of the
problem is the locked queuing up in poll_wait().
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://patch.msgid.link/20260516021852.256932-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
| -rw-r--r-- | fs/pipe.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/pipe.c b/fs/pipe.c index 9841648c9cf3..e37c79935ecb 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -664,7 +664,8 @@ pipe_poll(struct file *filp, poll_table *wait) union pipe_index idx; /* Epoll has some historical nasty semantics, this enables them */ - WRITE_ONCE(pipe->poll_usage, true); + if (unlikely(!READ_ONCE(pipe->poll_usage))) + WRITE_ONCE(pipe->poll_usage, true); /* * Reading pipe state only -- no need for acquiring the semaphore. |