linux-kernel - Re: [v7 5/5] mm, oom: cgroup v2 mount option to disable cgroup-aware OOM killer

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Message-ID: <20170907164245.GA21177@castle.DHCP.thefacebook.com>
Date:   Thu, 7 Sep 2017 17:42:45 +0100
From:   Roman Gushchin <guro@...com>
To:     Christopher Lameter <cl@...ux.com>
CC:     David Rientjes <rientjes@...gle.com>, <nzimmer@....com>,
        <holt@....com>, Michal Hocko <mhocko@...nel.org>,
        <linux-mm@...ck.org>, Vladimir Davydov <vdavydov.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, <kernel-team@...com>,
        <cgroups@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <sivanich@....com>
Subject: Re: [v7 5/5] mm, oom: cgroup v2 mount option to disable cgroup-aware
 OOM killer

On Thu, Sep 07, 2017 at 10:03:24AM -0500, Christopher Lameter wrote:
> On Thu, 7 Sep 2017, Roman Gushchin wrote:
> 
> > > Really? From what I know and worked on way back when: The reason was to be
> > > able to contain the affected application in a cpuset. Multiple apps may
> > > have been running in multiple cpusets on a large NUMA machine and the OOM
> > > condition in one cpuset should not affect the other. It also helped to
> > > isolate the application behavior causing the oom in numerous cases.
> > >
> > > Doesnt this requirement transfer to cgroups in the same way?
> >
> > We have per-node memory stats and plan to use them during the OOM victim
> > selection. Hopefully it can help.
> 
> One of the OOM causes could be that memory was restricted to a certain
> node set. Killing the allocating task is (was?) default behavior in that
> case so that the task that has the restrictions is killed. Not any task
> that may not have the restrictions and woiuld not experience OOM.

As I can see, it's not the default behavior these days. If we have a way
to select a victim between memcgs/tasks which are actually using
the corresponding type of memory, it's much better than to kill
an allocating task.