linux-kernel - Re: [patch] mm, oom: make a last minute check to prevent unnecessary memcg oom kills

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Date:   Tue, 17 Mar 2020 12:00:45 -0700
From:   Ami Fischman <fischman@...gle.com>
To:     Robert Kolchmeyer <rkolchmeyer@...gle.com>
Cc:     David Rientjes <rientjes@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [patch] mm, oom: make a last minute check to prevent unnecessary
 memcg oom kills

On Tue, Mar 17, 2020 at 11:26 AM Robert Kolchmeyer
<rkolchmeyer@...gle.com> wrote:
>
> On Tue, Mar 10, 2020 at 3:54 PM David Rientjes <rientjes@...gle.com> wrote:
> >
> > Robert, could you elaborate on the user-visible effects of this issue that
> > caused it to initially get reported?
>
> Ami (now cc'ed) knows more, but here is my understanding.

Robert's description of the mechanics we observed is accurate.

We discovered this regression in the oom-killer's behavior when
attempting to upgrade our system. The fraction of the system that
went unhealthy due to this issue was approximately equal to the
_sum_ of all other causes of unhealth, which are many and varied,
but each of which contribute only a small amount of
unhealth. This issue forced a rollback to the previous kernel
where we ~never see this behavior, returning our unhealth levels
to the previous background levels.

Cheers,
-a