linux-kernel - Re: [PATCH RFC] mm: don't raise MEMCG_OOM event due to failed high-order allocation

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Date:   Tue, 11 Sep 2018 14:41:04 +0200
From:   peter enderborg <peter.enderborg@...y.com>
To:     Michal Hocko <mhocko@...nel.org>, Roman Gushchin <guro@...com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <kernel-team@...com>, Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>
Subject: Re: [PATCH RFC] mm: don't raise MEMCG_OOM event due to failed
 high-order allocation

On 09/11/2018 02:11 PM, Michal Hocko wrote:
> Why is this a problem though? IIRC this event was deliberately placed
> outside of the oom path because we wanted to count allocation failures
> and this is also documented that way
>
>           oom
>                 The number of time the cgroup's memory usage was
>                 reached the limit and allocation was about to fail.
>
>                 Depending on context result could be invocation of OOM
>                 killer and retrying allocation or failing a
>
> One could argue that we do not apply the same logic to GFP_NOWAIT
> requests but in general I would like to see a good reason to change
> the behavior and if it is really the right thing to do then we need to
> update the documentation as well.
>

Why not introduce a MEMCG_ALLOC_FAIL in to memcg_memory_event?