From: Jan Kara <jack@suse.cz>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>, Jan Kara <jack@suse.cz>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] fs: Do not check if there is a fsnotify watcher on pseudo inodes
Date: Tue, 16 Jun 2020 09:47:01 +0200 [thread overview]
Message-ID: <20200616074701.GA20086@quack2.suse.cz> (raw)
In-Reply-To: <CAOQ4uxi0fqKFZ9=U-+DQ78233hR9TXEU44xRih4q=M556ynphA@mail.gmail.com>
On Mon 15-06-20 19:26:38, Amir Goldstein wrote:
> > This patch changes alloc_file_pseudo() to always opt out of fsnotify by
> > setting FMODE_NONOTIFY flag so that no check is made for fsnotify watchers
> > on pseudo files. This should be safe as the underlying helper for the
> > dentry is d_alloc_pseudo which explicitly states that no lookups are ever
> > performed meaning that fanotify should have nothing useful to attach to.
> >
> > The test motivating this was "perf bench sched messaging --pipe". On
> > a single-socket machine using threads the difference of the patch was
> > as follows.
> >
> > 5.7.0 5.7.0
> > vanilla nofsnotify-v1r1
> > Amean 1 1.3837 ( 0.00%) 1.3547 ( 2.10%)
> > Amean 3 3.7360 ( 0.00%) 3.6543 ( 2.19%)
> > Amean 5 5.8130 ( 0.00%) 5.7233 * 1.54%*
> > Amean 7 8.1490 ( 0.00%) 7.9730 * 2.16%*
> > Amean 12 14.6843 ( 0.00%) 14.1820 ( 3.42%)
> > Amean 18 21.8840 ( 0.00%) 21.7460 ( 0.63%)
> > Amean 24 28.8697 ( 0.00%) 29.1680 ( -1.03%)
> > Amean 30 36.0787 ( 0.00%) 35.2640 * 2.26%*
> > Amean 32 38.0527 ( 0.00%) 38.1223 ( -0.18%)
> >
> > The difference is small but in some cases it's outside the noise so
> > while marginal, there is still some small benefit to ignoring fsnotify
> > for files allocated via alloc_file_pseudo in some cases.
> >
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
>
> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Thanks for the patch Mel and for review Amir! I've added the patch to my
tree with small amendments to the changelog.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2020-06-16 7:47 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-15 12:13 [PATCH v2] fs: Do not check if there is a fsnotify watcher on pseudo inodes Mel Gorman
2020-06-15 16:26 ` Amir Goldstein
2020-06-15 17:25 ` Mel Gorman
2020-06-15 18:32 ` Amir Goldstein
2020-06-16 7:47 ` Jan Kara [this message]
2020-06-29 15:17 ` Eric Dumazet
2020-06-29 15:29 ` Mel Gorman
2020-06-29 18:48 ` Jan Kara
2020-06-19 8:51 ` [fs] 0587211dff: will-it-scale.per_thread_ops 4.7% improvement kernel test robot
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