From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f70.google.com (mail-wm0-f70.google.com [74.125.82.70]) by kanga.kvack.org (Postfix) with ESMTP id CBFC96B0005 for ; Tue, 30 Jan 2018 07:08:55 -0500 (EST) Received: by mail-wm0-f70.google.com with SMTP id t14so119291wmc.5 for ; Tue, 30 Jan 2018 04:08:55 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o21si7971171wrf.105.2018.01.30.04.08.54 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 30 Jan 2018 04:08:54 -0800 (PST) Date: Tue, 30 Jan 2018 13:08:52 +0100 From: Michal Hocko Subject: Re: [patch -mm v2 2/3] mm, memcg: replace cgroup aware oom killer mount option with tunable Message-ID: <20180130120852.GA21609@dhcp22.suse.cz> References: <20180125160016.30e019e546125bb13b5b6b4f@linux-foundation.org> <20180126143950.719912507bd993d92188877f@linux-foundation.org> <20180126161735.b999356fbe96c0acd33aaa66@linux-foundation.org> <20180129104657.GC21609@dhcp22.suse.cz> <20180129191139.GA1121507@devbig577.frc2.facebook.com> <20180130085445.GQ21609@dhcp22.suse.cz> <20180130115846.GA4720@castle.DHCP.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180130115846.GA4720@castle.DHCP.thefacebook.com> Sender: owner-linux-mm@kvack.org List-ID: To: Roman Gushchin Cc: Tejun Heo , Andrew Morton , David Rientjes , Vladimir Davydov , Johannes Weiner , Tetsuo Handa , kernel-team@fb.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org On Tue 30-01-18 11:58:51, Roman Gushchin wrote: > On Tue, Jan 30, 2018 at 09:54:45AM +0100, Michal Hocko wrote: > > On Mon 29-01-18 11:11:39, Tejun Heo wrote: > > Hello, Michal! > > > diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt > > index 2eaed1e2243d..67bdf19f8e5b 100644 > > --- a/Documentation/cgroup-v2.txt > > +++ b/Documentation/cgroup-v2.txt > > @@ -1291,8 +1291,14 @@ This affects both system- and cgroup-wide OOMs. For a cgroup-wide OOM > > the memory controller considers only cgroups belonging to the sub-tree > > of the OOM'ing cgroup. > > > > -The root cgroup is treated as a leaf memory cgroup, so it's compared > > -with other leaf memory cgroups and cgroups with oom_group option set. > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > IMO, this statement is important. Isn't it? > > > +Leaf cgroups are compared based on their cumulative memory usage. The > > +root cgroup is treated as a leaf memory cgroup as well, so it's > > +compared with other leaf memory cgroups. Due to internal implementation > > +restrictions the size of the root cgroup is a cumulative sum of > > +oom_badness of all its tasks (in other words oom_score_adj of each task > > +is obeyed). Relying on oom_score_adj (appart from OOM_SCORE_ADJ_MIN) > > +can lead to overestimating of the root cgroup consumption and it is > > Hm, and underestimating too. Also OOM_SCORE_ADJ_MIN isn't any different > in this case. Say, all tasks except a small one have OOM_SCORE_ADJ set to > -999, this means the root croup has extremely low chances to be elected. > > > +therefore discouraged. This might change in the future, though. > > Other than that looks very good to me. This? diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt index 2eaed1e2243d..34ad80ee90f2 100644 --- a/Documentation/cgroup-v2.txt +++ b/Documentation/cgroup-v2.txt @@ -1291,8 +1291,15 @@ This affects both system- and cgroup-wide OOMs. For a cgroup-wide OOM the memory controller considers only cgroups belonging to the sub-tree of the OOM'ing cgroup. -The root cgroup is treated as a leaf memory cgroup, so it's compared -with other leaf memory cgroups and cgroups with oom_group option set. +Leaf cgroups and cgroups with oom_group option set are compared based +on their cumulative memory usage. The root cgroup is treated as a +leaf memory cgroup as well, so it's compared with other leaf memory +cgroups. Due to internal implementation restrictions the size of +the root cgroup is a cumulative sum of oom_badness of all its tasks +(in other words oom_score_adj of each task is obeyed). Relying on +oom_score_adj (appart from OOM_SCORE_ADJ_MIN) can lead to over or +underestimating of the root cgroup consumption and it is therefore +discouraged. This might change in the future, though. If there are no cgroups with the enabled memory controller, the OOM killer is using the "traditional" process-based approach. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org