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 F32DDC433E1 for ; Wed, 26 Aug 2020 11:45:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2806C20707 for ; Wed, 26 Aug 2020 11:45:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2806C20707 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 88D806B0003; Wed, 26 Aug 2020 07:45:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 83E166B0005; Wed, 26 Aug 2020 07:45:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 77B696B0006; Wed, 26 Aug 2020 07:45:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0117.hostedemail.com [216.40.44.117]) by kanga.kvack.org (Postfix) with ESMTP id 606E06B0003 for ; Wed, 26 Aug 2020 07:45:13 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 19346181AEF1A for ; Wed, 26 Aug 2020 11:45:13 +0000 (UTC) X-FDA: 77192538906.24.music17_320cf4227064 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id D20651A4A0 for ; Wed, 26 Aug 2020 11:45:12 +0000 (UTC) X-HE-Tag: music17_320cf4227064 X-Filterd-Recvd-Size: 2645 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Wed, 26 Aug 2020 11:45:11 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04392;MF=xlpang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0U6vmqQL_1598442306; Received: from xunleideMacBook-Pro.local(mailfrom:xlpang@linux.alibaba.com fp:SMTPD_---0U6vmqQL_1598442306) by smtp.aliyun-inc.com(127.0.0.1); Wed, 26 Aug 2020 19:45:07 +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> From: xunlei Message-ID: <5b22890d-190f-be1d-3be8-995765dbb957@linux.alibaba.com> Date: Wed, 26 Aug 2020 19:45:06 +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: <20200826110015.GO22869@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 X-Rspamd-Queue-Id: D20651A4A0 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020/8/26 =E4=B8=8B=E5=8D=887:00, Michal Hocko wrote: > On Wed 26-08-20 18:41:18, xunlei wrote: >> On 2020/8/26 =E4=B8=8B=E5=8D=884:11, Michal Hocko wrote: >>> On Wed 26-08-20 15:27:02, Xunlei Pang wrote: >>>> We've met softlockup with "CONFIG_PREEMPT_NONE=3Dy", 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. >=20 > OK, you made me more curious. If this is a tiny guest and this is a har= d > 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 setu= p > that it causes soft lockups? >=20 oom_status =3D mem_cgroup_oom(mem_over_limit, gfp_mask, get_order(nr_pages * PAGE_SIZE)); switch (oom_status) { case OOM_SUCCESS: nr_retries =3D MAX_RECLAIM_RETRIES; goto retry; It retries here endlessly, because oom reaper has no cpu to schedule.