linux-kernel - Re: memleak in cgroup

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Date:   Tue, 28 Apr 2020 17:10:33 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Roman Gushchin <guro@...com>, Johannes Weiner <hannes@...xchg.org>
CC:     <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

Hi,

On 2020/4/28 1:24, Roman Gushchin wrote:
> 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 re-tested in 5.7-rc3, it has same problem and the 
/sys/fs/cgroup/unified/cgroup.stat afther test is:

nr_descendants 50
nr_dying_descendants 0

> 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?
config and dmesg are attached.
>
> Thanks!

View attachment "config" of type "text/plain" (157249 bytes)

View attachment "dmesg" of type "text/plain" (282802 bytes)