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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 5DAA2C43461 for ; Mon, 14 Sep 2020 04:15:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 18CCB20771 for ; Mon, 14 Sep 2020 04:15:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726020AbgINEPe (ORCPT ); Mon, 14 Sep 2020 00:15:34 -0400 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:50838 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725974AbgINEPc (ORCPT ); Mon, 14 Sep 2020 00:15:32 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R521e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04395;MF=xlpang@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0U8ps8Kn_1600056928; Received: from xunleideMacBook-Pro.local(mailfrom:xlpang@linux.alibaba.com fp:SMTPD_---0U8ps8Kn_1600056928) by smtp.aliyun-inc.com(127.0.0.1); Mon, 14 Sep 2020 12:15:28 +0800 Reply-To: xlpang@linux.alibaba.com Subject: Re: [PATCH] mm: memcg: yield cpu when we fail to charge pages To: Julius Hemanth Pitti , hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, xe-linux-external@cisco.com References: <20200908185051.62420-1-jpitti@cisco.com> From: Xunlei Pang Message-ID: Date: Mon, 14 Sep 2020 12:15:27 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200908185051.62420-1-jpitti@cisco.com> Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/9/9 AM2:50, Julius Hemanth Pitti wrote: > For non root CG, in try_charge(), we keep trying > to charge until we succeed. On non-preemptive > kernel, when we are OOM, this results in holding > CPU forever. > > On SMP systems, this doesn't create a big problem > because oom_reaper get a change to kill victim > and make some free pages. However on a single-core > CPU (or cases where oom_reaper pinned to same CPU > where try_charge is executing), oom_reaper shall > never get scheduled and we stay in try_charge forever. > > Steps to repo this on non-smp: > 1. mount -t tmpfs none /sys/fs/cgroup > 2. mkdir /sys/fs/cgroup/memory > 3. mount -t cgroup none /sys/fs/cgroup/memory -o memory > 4. mkdir /sys/fs/cgroup/memory/0 > 5. echo 40M > /sys/fs/cgroup/memory/0/memory.limit_in_bytes > 6. echo $$ > /sys/fs/cgroup/memory/0/tasks > 7. stress -m 5 --vm-bytes 10M --vm-hang 0 > > Signed-off-by: Julius Hemanth Pitti > --- > mm/memcontrol.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 0d6f3ea86738..4620d70267cb 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2652,6 +2652,8 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, > if (fatal_signal_pending(current)) > goto force; > > + cond_resched(); > + > /* > * keep retrying as long as the memcg oom killer is able to make > * a forward progress or bypass the charge if the oom killer > This should be fixed by: https://lkml.org/lkml/2020/8/26/1440 Thanks, Xunlei