From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 7E5B38E00D7 for ; Fri, 25 Jan 2019 12:24:20 -0500 (EST) Received: by mail-ed1-f72.google.com with SMTP id s50so3938898edd.11 for ; Fri, 25 Jan 2019 09:24:20 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id i46si6749425eda.288.2019.01.25.09.24.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 25 Jan 2019 09:24:18 -0800 (PST) Date: Fri, 25 Jan 2019 18:24:16 +0100 From: Michal Hocko Subject: Re: + memcg-do-not-report-racy-no-eligible-oom-tasks.patch added to -mm tree Message-ID: <20190125172416.GB20411@dhcp22.suse.cz> References: <20190109190306.rATpT%akpm@linux-foundation.org> <20190125165624.GA17719@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190125165624.GA17719@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: akpm@linux-foundation.org, mm-commits@vger.kernel.org, penguin-kernel@i-love.sakura.ne.jp, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Fri 25-01-19 11:56:24, Johannes Weiner wrote: > On Wed, Jan 09, 2019 at 11:03:06AM -0800, akpm@linux-foundation.org wrote: > > > > The patch titled > > Subject: memcg: do not report racy no-eligible OOM tasks > > has been added to the -mm tree. Its filename is > > memcg-do-not-report-racy-no-eligible-oom-tasks.patch > > > > This patch should soon appear at > > http://ozlabs.org/~akpm/mmots/broken-out/memcg-do-not-report-racy-no-eligible-oom-tasks.patch > > and later at > > http://ozlabs.org/~akpm/mmotm/broken-out/memcg-do-not-report-racy-no-eligible-oom-tasks.patch > > > > Before you just go and hit "reply", please: > > a) Consider who else should be cc'ed > > b) Prefer to cc a suitable mailing list as well > > c) Ideally: find the original patch on the mailing list and do a > > reply-to-all to that, adding suitable additional cc's > > > > *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** > > > > The -mm tree is included into linux-next and is updated > > there every 3-4 working days > > > > ------------------------------------------------------ > > From: Michal Hocko > > Subject: memcg: do not report racy no-eligible OOM tasks > > > > Tetsuo has reported [1] that a single process group memcg might easily > > swamp the log with no-eligible oom victim reports due to race between the > > memcg charge and oom_reaper > > > > Thread 1 Thread2 oom_reaper > > try_charge try_charge > > mem_cgroup_out_of_memory > > mutex_lock(oom_lock) > > mem_cgroup_out_of_memory > > mutex_lock(oom_lock) > > out_of_memory > > select_bad_process > > oom_kill_process(current) > > wake_oom_reaper > > oom_reap_task > > MMF_OOM_SKIP->victim > > mutex_unlock(oom_lock) > > out_of_memory > > select_bad_process # no task > > > > If Thread1 didn't race it would bail out from try_charge and force the > > charge. We can achieve the same by checking tsk_is_oom_victim inside the > > oom_lock and therefore close the race. > > > > [1] http://lkml.kernel.org/r/bb2074c0-34fe-8c2c-1c7d-db71338f1e7f@i-love.sakura.ne.jp > > Link: http://lkml.kernel.org/r/20190107143802.16847-3-mhocko@kernel.org > > Signed-off-by: Michal Hocko > > Cc: Tetsuo Handa > > Cc: Johannes Weiner > > Signed-off-by: Andrew Morton > > It looks like this problem is happening in production systems: > > https://www.spinics.net/lists/cgroups/msg21268.html > > where the threads don't exit because they are trapped writing out the > oom messages to a slow console (running the reproducer from this email > thread triggers the oom flooding). > > So IMO we should put this into 5.0 and add: Please note that Tetsuo has found out that this will not work with the CLONE_VM without CLONE_SIGHAND cases and his http://lkml.kernel.org/r/01370f70-e1f6-ebe4-b95e-0df21a0bc15e@i-love.sakura.ne.jp should handle this case as well. I've only had objections to the changelog but other than that the patch looked sensible to me. -- Michal Hocko SUSE Labs