linux-kernel - Re: memleak in cgroup

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Message-ID: <20200427172421.GA122591@carbon.DHCP.thefacebook.com>
Date:   Mon, 27 Apr 2020 10:24:21 -0700
From:   Roman Gushchin <guro@...com>
To:     Johannes Weiner <hannes@...xchg.org>
CC:     Yang Yingliang <yangyingliang@...wei.com>, <tj@...nel.org>,
        <lizefan@...wei.com>, <cgroups@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <wangkefeng.wang@...wei.com>,
        <linux-mm@...ck.org>, <guro@...xchg.org>
Subject: Re: memleak in cgroup

On Mon, Apr 27, 2020 at 01:13:04PM -0400, Johannes Weiner wrote:
> +cc Roman who has been looking the most at this area
> 
> On Mon, Apr 27, 2020 at 03:48:13PM +0800, Yang Yingliang wrote:
> > +cc linux-mm@...ck.org <mailto:linux-mm@...ck.org>
> > 
> > On 2020/4/26 19:21, Yang Yingliang wrote:
> > > Hi,
> > > 
> > > When I doing the follow test in kernel-5.7-rc2, I found mem-free is
> > > decreased
> > > 
> > > #!/bin/sh
> > > cd /sys/fs/cgroup/memory/
> > > 
> > > for((i=0;i<45;i++))
> > > do
> > >         for((j=0;j<60000;j++))
> > >         do
> > >                 mkdir /sys/fs/cgroup/memory/yyl-cg$j
> > >         done
> > >         sleep 1
> > >         ls /sys/fs/cgroup/memory/ | grep yyl | xargs rmdir
> > > done
> 
> Should be easy enough to reproduce, thanks for the report. I'll try to
> take a look later this week, unless Roman beats me to it.
> 
> Is this a new observation in 5.7-rc2?
> 
> Can you provide /sys/fs/cgroup/unified/cgroup.stat after the test?

I'm actually trying to reproduce it now, but so far haven't found any issues.

Yang, can you, please, attach the config you're using?

And also confirm that you're giving the system some time before looking
at the memory statistics? Reclaim of internal cgroup structure is a complex
process which might take some time to finish.

Is dmesg also clean?

Thanks!