Re: [PATCH v3] fsnotify: optimize the case of no parent watcher

[Jan Kara <jack@suse.cz>]

On Tue 16-01-24 14:53:00, Amir Goldstein wrote:
> On Tue, Jan 16, 2024 at 2:04 PM Jan Kara <jack@suse.cz> 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@kernel.dk>
> > > Link: https://lore.kernel.org/linux-fsdevel/b45bd8ff-5654-4e67-90a6-aad5e6759e0b@kernel.dk/
> > > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > > ---
> > >
> > > 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.

Merged your improvement now (and I've split off the cleanup into a separate
change and dropped the creation of fsnotify_path() which seemed a bit
pointless with a single caller). All pushed out.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR