From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 78C62C47247 for ; Wed, 6 May 2020 01:50:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F9912073B for ; Wed, 6 May 2020 01:50:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729894AbgEFBuy (ORCPT ); Tue, 5 May 2020 21:50:54 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:3851 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728069AbgEFBuy (ORCPT ); Tue, 5 May 2020 21:50:54 -0400 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 7772AED51D9EDAEEF549; Wed, 6 May 2020 09:50:52 +0800 (CST) Received: from [127.0.0.1] (10.166.215.99) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.487.0; Wed, 6 May 2020 09:50:44 +0800 Subject: Re: cgroup pointed by sock is leaked on mode switch To: Tejun Heo CC: , , , "Libin (Huawei)" , , , References: <03dab6ab-0ffe-3cae-193f-a7f84e9b14c5@huawei.com> <20200505160639.GG12217@mtj.thefacebook.com> From: Yang Yingliang Message-ID: Date: Wed, 6 May 2020 09:50:43 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200505160639.GG12217@mtj.thefacebook.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.166.215.99] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +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. >