From: Yang Yingliang <yangyingliang@huawei.com>
To: Tejun Heo <tj@kernel.org>
Cc: <linux-kernel@vger.kernel.org>, <cgroups@vger.kernel.org>,
<netdev@vger.kernel.org>,
"Libin (Huawei)" <huawei.libin@huawei.com>, <guofan5@huawei.com>,
<wangkefeng.wang@huawei.com>, <lizefan@huawei.com>
Subject: Re: cgroup pointed by sock is leaked on mode switch
Date: Wed, 6 May 2020 09:50:43 +0800 [thread overview]
Message-ID: <c9879fd2-cb91-2a08-8293-c6a436b5a539@huawei.com> (raw)
In-Reply-To: <20200505160639.GG12217@mtj.thefacebook.com>
+cc lizefan@huawei.com
On 2020/5/6 0:06, Tejun Heo wrote:
> Hello, Yang.
>
> On Sat, May 02, 2020 at 06:27:21PM +0800, Yang Yingliang wrote:
>> I find the number nr_dying_descendants is increasing:
>> linux-dVpNUK:~ # find /sys/fs/cgroup/ -name cgroup.stat -exec grep
>> '^nr_dying_descendants [^0]' {} +
>> /sys/fs/cgroup/unified/cgroup.stat:nr_dying_descendants 80
>> /sys/fs/cgroup/unified/system.slice/cgroup.stat:nr_dying_descendants 1
>> /sys/fs/cgroup/unified/system.slice/system-hostos.slice/cgroup.stat:nr_dying_descendants
>> 1
>> /sys/fs/cgroup/unified/lxc/cgroup.stat:nr_dying_descendants 79
>> /sys/fs/cgroup/unified/lxc/5f1fdb8c54fa40c3e599613dab6e4815058b76ebada8a27bc1fe80c0d4801764/cgroup.stat:nr_dying_descendants
>> 78
>> /sys/fs/cgroup/unified/lxc/5f1fdb8c54fa40c3e599613dab6e4815058b76ebada8a27bc1fe80c0d4801764/system.slice/cgroup.stat:nr_dying_descendants
>> 78
> Those numbers are nowhere close to causing oom issues. There are some
> aspects of page and other cache draining which is being improved but unless
> you're seeing numbers multiple orders of magnitude higher, this isn't the
> source of your problem.
>
>> The situation is as same as the commit bd1060a1d671 ("sock, cgroup: add
>> sock->sk_cgroup") describes.
>> "On mode switch, cgroup references which are already being pointed to by
>> socks may be leaked."
> I'm doubtful that you're hitting that issue. Mode switching means memcg
> being switched between cgroup1 and cgroup2 hierarchies, which is unlikely to
> be what's happening when you're launching docker containers.
>
> The first step would be identifying where memory is going and finding out
> whether memcg is actually being switched between cgroup1 and 2 - look at the
> hierarchy number in /proc/cgroups, if that's switching between 0 and
> someting not zero, it is switching.
>
> Thanks.
>
next prev parent reply other threads:[~2020-05-06 1:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-02 10:27 cgroup pointed by sock is leaked on mode switch Yang Yingliang
2020-05-05 16:06 ` Tejun Heo
2020-05-06 1:50 ` Yang Yingliang [this message]
2020-05-06 2:16 ` Zefan Li
2020-05-06 7:51 ` Zefan Li
2020-05-09 2:31 ` Yang Yingliang
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