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

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Message-ID: <54d56b12-3f75-1382-cc12-a8e63e24ce1f@I-love.SAKURA.ne.jp>
Date:   Wed, 11 Mar 2020 20:41:45 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Robert Kolchmeyer <rkolchmeyer@...gle.com>,
        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 2020/03/11 7:54, David Rientjes wrote:
> The patch certainly prevents unnecessary oom kills when there is a pending 
> victim that uncharges its memory between invoking the oom killer and 
> finding MMF_OOM_SKIP in the list of eligible tasks and its much more 
> common on systems with limited cpu cores.

I think that it is dump_header() which currently spends much time (due to
synchronous printing) enough to make "the second memcg oom kill shows usage
is >40MB below its limit of 100MB" happen. Shouldn't we call dump_header()
and then do the last check and end with "but did not kill anybody" message?