linux-kernel - Re: [v8 0/4] cgroup-aware OOM killer

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Date:   Thu, 21 Sep 2017 01:30:45 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Roman Gushchin <guro@...com>
cc:     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
Subject: Re: [v8 0/4] cgroup-aware OOM killer

On Mon, 18 Sep 2017, Roman Gushchin wrote:

> > As said in other email. We can make priorities hierarchical (in the same
> > sense as hard limit or others) so that children cannot override their
> > parent.
> 
> You mean they can set the knob to any value, but parent's value is enforced,
> if it's greater than child's value?
> 
> If so, this sounds logical to me. Then we have size-based comparison and
> priority-based comparison with similar rules, and all use cases are covered.
> 
> Ok, can we stick with this design?
> Then I'll return oom_priorities in place, and post a (hopefully) final version.
> 

I just want to make sure that we are going with your original 
implementation here: that oom_priority is only effective for compare 
sibling memory cgroups and nothing beyond that.  The value alone has no 
relationship to any ancestor.  We can't set oom_priority based on the 
priorities of any other memory cgroups other than our own siblings because 
we have no control over how those change.