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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 35CC7C433E2 for ; Tue, 8 Sep 2020 20:53:15 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C3CD92166E for ; Tue, 8 Sep 2020 20:53:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C3CD92166E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A49EB6B005C; Tue, 8 Sep 2020 16:53:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A014B6B0062; Tue, 8 Sep 2020 16:53:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 90FAC6B006C; Tue, 8 Sep 2020 16:53:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0242.hostedemail.com [216.40.44.242]) by kanga.kvack.org (Postfix) with ESMTP id 7FCFD6B005C for ; Tue, 8 Sep 2020 16:53:13 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 347593628 for ; Tue, 8 Sep 2020 20:53:13 +0000 (UTC) X-FDA: 77241094266.03.women75_2517760270d7 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id 08E6A28A4E9 for ; Tue, 8 Sep 2020 20:53:13 +0000 (UTC) X-HE-Tag: women75_2517760270d7 X-Filterd-Recvd-Size: 3748 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf24.hostedemail.com (Postfix) with ESMTP for ; Tue, 8 Sep 2020 20:53:12 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 02C86ADC5; Tue, 8 Sep 2020 20:53:12 +0000 (UTC) Date: Tue, 8 Sep 2020 22:53:10 +0200 From: Michal Hocko To: Yang Shi Cc: Julius Hemanth Pitti , Johannes Weiner , Vladimir Davydov , Andrew Morton , Roman Gushchin , Cgroups , Linux MM , Linux Kernel Mailing List , xe-linux-external@cisco.com Subject: Re: [PATCH v2] mm: memcg: yield cpu when we fail to charge pages Message-ID: <20200908205310.GF26850@dhcp22.suse.cz> References: <20200908201426.14837-1-jpitti@cisco.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 08E6A28A4E9 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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 Tue 08-09-20 13:31:51, Yang Shi wrote: > On Tue, Sep 8, 2020 at 1:14 PM 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 > > Isn't it the same problem solved by e3336cab2579 ("mm: memcg: fix > memcg reclaim soft lockup")? It has been in Linus's tree. Yes it should because it adds a scheduling point regardless of reclaimability. > > Signed-off-by: Julius Hemanth Pitti > > Acked-by: Roman Gushchin > > --- > > > > Changes in v2: > > - Added comments. > > - Added "Acked-by: Roman Gushchin ". > > --- > > mm/memcontrol.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index cfa6cbad21d5..4f293bf8c7ed 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2745,6 +2745,15 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, > > if (fatal_signal_pending(current)) > > goto force; > > > > + /* > > + * We failed to charge even after retries, give oom_reaper or > > + * other process a change to make some free pages. > > + * > > + * On non-preemptive, Non-SMP system, this is critical, else > > + * we keep retrying with no success, forever. > > + */ > > + 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 > > -- > > 2.17.1 > > > > -- Michal Hocko SUSE Labs