linux-kernel - Re: [PATCH] memcg, oom: move out_of

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Message-Id: <xr93bmbtju6f.fsf@gthelen.svl.corp.google.com>
Date:   Fri, 29 Jun 2018 11:59:04 -0700
From:   Greg Thelen <gthelen@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg, oom: move out_of_memory back to the charge path

Michal Hocko <mhocko@...nel.org> wrote:

> On Thu 28-06-18 16:19:07, Greg Thelen wrote:
>> Michal Hocko <mhocko@...nel.org> wrote:
> [...]
>> > +	if (mem_cgroup_out_of_memory(memcg, mask, order))
>> > +		return OOM_SUCCESS;
>> > +
>> > +	WARN(1,"Memory cgroup charge failed because of no reclaimable memory! "
>> > +		"This looks like a misconfiguration or a kernel bug.");
>> 
>> I'm not sure here if the warning should here or so strongly worded.  It
>> seems like the current task could be oom reaped with MMF_OOM_SKIP and
>> thus mem_cgroup_out_of_memory() will return false.  So there's nothing
>> alarming in that case.
>
> If the task is reaped then its charges should be released as well and
> that means that we should get below the limit. Sure there is some room
> for races but this should be still unlikely. Maybe I am just
> underestimating though.
>
> What would you suggest instead?

I suggest checking MMF_OOM_SKIP or deleting the warning.  But I don't
feel strongly.