On Wed, Oct 16, 2024 at 03:10:34PM +0200, Christian Brauner wrote:
On Fri, 26 Apr 2024 16:05:48 +0800, Xuewen Yan wrote:
Now, the epoll only use wake_up() interface to wake up task. However, sometimes, there are epoll users which want to use the synchronous wakeup flag to hint the scheduler, such as Android binder driver. So add a wake_up_sync() define, and use the wake_up_sync() when the sync is true in ep_poll_callback().
[...]
Applied to the vfs.misc branch of the vfs/vfs.git tree. Patches in the vfs.misc branch should appear in linux-next soon.
Please report any outstanding bugs that were missed during review in a new review to the original patch series allowing us to drop it.
It's encouraged to provide Acked-bys and Reviewed-bys even though the patch has now been applied. If possible patch trailers will be updated.
Note that commit hashes shown below are subject to change due to rebase, trailer updates or similar. If in doubt, please check the listed branch.
tree: https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git branch: vfs.misc
This is a bug that's been present for all of time, so I think we should:
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org
I sent a patch which adds a benchmark for nonblocking pipes using epoll: https://lore.kernel.org/lkml/20241016190009.866615-1-bgeffon@google.com/
Using this new benchmark I get the following results without this fix and with this fix:
$ tools/perf/perf bench sched pipe -n # Running 'sched/pipe' benchmark: # Executed 1000000 pipe operations between two processes
Total time: 12.194 [sec]
12.194376 usecs/op 82005 ops/sec
$ tools/perf/perf bench sched pipe -n # Running 'sched/pipe' benchmark: # Executed 1000000 pipe operations between two processes
Total time: 9.229 [sec]
9.229738 usecs/op 108345 ops/sec
[1/1] epoll: Add synchronous wakeup support for ep_poll_callback https://git.kernel.org/vfs/vfs/c/2ce0e17660a7