linux-kernel - Re: [v9 3/5] mm, oom: cgroup-aware OOM killer

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Date:   Wed, 4 Oct 2017 16:04:52 +0100
From:   Roman Gushchin <guro@...com>
To:     Michal Hocko <mhocko@...nel.org>
CC:     <linux-mm@...ck.org>, Vladimir Davydov <vdavydov.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        David Rientjes <rientjes@...gle.com>,
        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>
Subject: Re: [v9 3/5] mm, oom: cgroup-aware OOM killer

On Tue, Oct 03, 2017 at 04:22:46PM +0200, Michal Hocko wrote:
> On Tue 03-10-17 15:08:41, Roman Gushchin wrote:
> > On Tue, Oct 03, 2017 at 03:36:23PM +0200, Michal Hocko wrote:
> [...]
> > > I guess we want to inherit the value on the memcg creation but I agree
> > > that enforcing parent setting is weird. I will think about it some more
> > > but I agree that it is saner to only enforce per memcg value.
> > 
> > I'm not against, but we should come up with a good explanation, why we're
> > inheriting it; or not inherit.
> 
> Inheriting sounds like a less surprising behavior. Once you opt in for
> oom_group you can expect that descendants are going to assume the same
> unless they explicitly state otherwise.

Not sure I understand why. Setting memory.oom_group on a child memcg
has absolutely no meaning until memory.max is also set. In case of OOM
scoped to the parent memcg or above, parent's value defines the behavior.

If a user decides to create a separate OOM domain (be setting the hard
memory limit), he/she can also make a decision on how OOM event should
be handled.

Thanks!