From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: [GIT PULL] cgroup changes for v4.18-rc1
Date: Wed, 6 Jun 2018 08:22:26 -0700
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Li Zefan <lizefan@huawei.com>, Johannes Weiner <hannes@cmpxchg.org>, cgroups <cgroups@vger.kernel.org>

On Wed, Jun 06, 2018 at 08:14:27AM -0700, Linus Torvalds wrote:
> On Wed, Jun 6, 2018 at 8:04 AM Tejun Heo <tj@kernel.org> wrote:
> >
> > The notification implementation isn't super light weight, so the patch
> > ratelimits the notifications by capping minimum notification interval
> > interval to 10ms.
> 
> Yeah, I looked at the patch (and the code) to make sense of the explanation.
> 
> My reaction to that was that it might be a better idea to simply not
> notify if a notification was already pending, rather than have the
> timeout. Or perhaps in addition to. The path _to_ the fsnotify code
> looked quite messy, though.

Yeah, getting to the inode is currently quite involved.  Some of the
complications come from the fact that a kernfs node can be associated
with multiple inodes for sysfs namespace support.

The right thing to do could be linking the inodes to the kernfs node
and protect it with a spinlock so that we don't have to punt and walk
them directly from notification path.

For now, I think the 10ms thing is an acceptable workaround but this
likely needs more work in the future.

Thanks.

-- 
tejun