On Tue, Jan 16, 2024 at 2:04 PM Jan Kara <jack@xxxxxxx> wrote: > > On Tue 16-01-24 13:32:47, Amir Goldstein wrote: > > If parent inode is not watching, check for the event in masks of > > sb/mount/inode masks early to optimize out most of the code in > > __fsnotify_parent() and avoid calling fsnotify(). > > > > Jens has reported that this optimization improves BW and IOPS in an > > io_uring benchmark by more than 10% and reduces perf reported CPU usage. > > > > before: > > > > + 4.51% io_uring [kernel.vmlinux] [k] fsnotify > > + 3.67% io_uring [kernel.vmlinux] [k] __fsnotify_parent > > > > after: > > > > + 2.37% io_uring [kernel.vmlinux] [k] __fsnotify_parent > > > > Reported-and-tested-by: Jens Axboe <axboe@xxxxxxxxx> > > Link: https://lore.kernel.org/linux-fsdevel/b45bd8ff-5654-4e67-90a6-aad5e6759e0b@xxxxxxxxx/ > > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> > > --- > > > > Jan, > > > > Considering that this change looks like a clear win and it actually > > the change that you suggested, I cleaned it up a bit and posting for > > your consideration. > > Agreed, I like this. What did you generate this patch against? It does not > apply on top of current Linus' tree (maybe it needs the change sitting in > VFS tree - which is fine I can wait until that gets merged)? > Yes, it is on top of Christian's vfs-fixes branch. > > I've kept the wrappers fsnotify_path() and fsnotify_sb_has_watchers() > > although they are not directly related to the optimization, because they > > makes the code a bit nicer IMO. > > Yeah, these cleanups are fine. I would have prefered them as a separate > patch (some people might want the performance improvement to be backported > and this makes it unnecessarily more complex) but don't resend just because > of that. > Makes sense. Thanks, Amir.
