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=-7.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,UNPARSEABLE_RELAY,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 1EC99C433E1 for ; Wed, 26 Aug 2020 12:21:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBB312080C for ; Wed, 26 Aug 2020 12:21:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729473AbgHZMVp (ORCPT ); Wed, 26 Aug 2020 08:21:45 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:55028 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729263AbgHZMVm (ORCPT ); Wed, 26 Aug 2020 08:21:42 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R321e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01419;MF=xlpang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0U6vWez3_1598444499; Received: from xunleideMacBook-Pro.local(mailfrom:xlpang@linux.alibaba.com fp:SMTPD_---0U6vWez3_1598444499) by smtp.aliyun-inc.com(127.0.0.1); Wed, 26 Aug 2020 20:21:39 +0800 Reply-To: xlpang@linux.alibaba.com Subject: Re: [PATCH] mm: memcg: Fix memcg reclaim soft lockup To: Michal Hocko Cc: Johannes Weiner , Andrew Morton , Vladimir Davydov , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <1598426822-93737-1-git-send-email-xlpang@linux.alibaba.com> <20200826081102.GM22869@dhcp22.suse.cz> <99efed0e-050a-e313-46ab-8fe6228839d5@linux.alibaba.com> <20200826110015.GO22869@dhcp22.suse.cz> <20200826120740.GP22869@dhcp22.suse.cz> From: xunlei Message-ID: <19eb48db-7d5e-0f55-5dfc-6a71274fd896@linux.alibaba.com> Date: Wed, 26 Aug 2020 20:21:39 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200826120740.GP22869@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/8/26 下午8:07, Michal Hocko wrote: > On Wed 26-08-20 20:00:47, xunlei wrote: >> On 2020/8/26 下午7:00, Michal Hocko wrote: >>> On Wed 26-08-20 18:41:18, xunlei wrote: >>>> On 2020/8/26 下午4:11, Michal Hocko wrote: >>>>> On Wed 26-08-20 15:27:02, Xunlei Pang wrote: >>>>>> We've met softlockup with "CONFIG_PREEMPT_NONE=y", when >>>>>> the target memcg doesn't have any reclaimable memory. >>>>> >>>>> Do you have any scenario when this happens or is this some sort of a >>>>> test case? >>>> >>>> It can happen on tiny guest scenarios. >>> >>> OK, you made me more curious. If this is a tiny guest and this is a hard >>> limit reclaim path then we should trigger an oom killer which should >>> kill the offender and that in turn bail out from the try_charge lopp >>> (see should_force_charge). So how come this repeats enough in your setup >>> that it causes soft lockups? >>> >> >> should_force_charge() is false, the current trapped in endless loop is >> not the oom victim. > > How is that possible? If the oom killer kills a task and that doesn't > resolve the oom situation then it would go after another one until all > tasks are killed. Or is your task living outside of the memcg it tries > to charge? > All tasks are in memcgs. Looks like the first oom victim is not finished (unable to schedule), later mem_cgroup_oom()->...->oom_evaluate_task() will set oc->chosen to -1 and abort.