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 B9D53C433DF for ; Wed, 26 Aug 2020 11:54:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7AB8B2080C for ; Wed, 26 Aug 2020 11:54:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7AB8B2080C 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 1AB766B0006; Wed, 26 Aug 2020 07:54:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 15C1D6B0007; Wed, 26 Aug 2020 07:54:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 071C06B0008; Wed, 26 Aug 2020 07:54:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0033.hostedemail.com [216.40.44.33]) by kanga.kvack.org (Postfix) with ESMTP id E0D336B0006 for ; Wed, 26 Aug 2020 07:54:42 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 9518F1DEC for ; Wed, 26 Aug 2020 11:54:42 +0000 (UTC) X-FDA: 77192562804.11.flag96_491595e27064 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin11.hostedemail.com (Postfix) with ESMTP id 6806A180F8B82 for ; Wed, 26 Aug 2020 11:54:42 +0000 (UTC) X-HE-Tag: flag96_491595e27064 X-Filterd-Recvd-Size: 2947 Received: from out30-42.freemail.mail.aliyun.com (out30-42.freemail.mail.aliyun.com [115.124.30.42]) by imf28.hostedemail.com (Postfix) with ESMTP for ; Wed, 26 Aug 2020 11:54:41 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R431e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04427;MF=xlpang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0U6vV5Ro_1598442870; Received: from xunleideMacBook-Pro.local(mailfrom:xlpang@linux.alibaba.com fp:SMTPD_---0U6vV5Ro_1598442870) by smtp.aliyun-inc.com(127.0.0.1); Wed, 26 Aug 2020 19:54:31 +0800 Reply-To: xlpang@linux.alibaba.com Subject: Re: [PATCH] mm: memcg: Fix memcg reclaim soft lockup From: Xunlei Pang 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> <5b22890d-190f-be1d-3be8-995765dbb957@linux.alibaba.com> Message-ID: <0cf41b39-f039-7e53-ea80-9d5d0c784e73@linux.alibaba.com> Date: Wed, 26 Aug 2020 19:54:30 +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: <5b22890d-190f-be1d-3be8-995765dbb957@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 X-Rspamd-Queue-Id: 6806A180F8B82 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, 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=887:45, xunlei wrote: > 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. >> >> OK, you made me more curious. If this is a tiny guest and this is a ha= rd >> 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 set= up >> 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; Actually we can add "cond_resched()" here, but I think it's better to have one at the memcg reclaim path to avoid other unexpected issues. > goto retry; >=20 > It retries here endlessly, because oom reaper has no cpu to schedule. >=20