linux-kernel - Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task

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Date:   Mon, 18 Oct 2021 22:34:02 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Vasily Averin <vvs@...tuozzo.com>
Cc:     Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        Uladzislau Rezki <urezki@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Cgroups <cgroups@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel@...nvz.org
Subject: Re: [PATCH memcg 0/1] false global OOM triggered by memcg-limited task

On Mon, Oct 18, 2021 at 12:19 PM Vasily Averin <vvs@...tuozzo.com> wrote:
>
> On 18.10.2021 21:52, Vasily Averin wrote:
> > On 18.10.2021 18:07, Shakeel Butt wrote:
> >> On Mon, Oct 18, 2021 at 5:27 AM Michal Hocko <mhocko@...e.com> wrote:
> >>>
> >>> [restore the cc list]
> >>>
> >>> On Mon 18-10-21 15:14:26, Vasily Averin wrote:
> >>>> On 18.10.2021 14:53, Michal Hocko wrote:
> >>>>> On Mon 18-10-21 13:05:35, Vasily Averin wrote:
> >>>>>> On 18.10.2021 12:04, Michal Hocko wrote:
> >>>>>> Here we call try_charge_memcg() that return success and approve the allocation,
> >>>>>> however then we hit into kmem limit and fail the allocation.
> >>>>>
> >>>>> Just to make sure I understand this would be for the v1 kmem explicit
> >>>>> limit, correct?
> >>>>
> >>>> yes, I mean this limit.
> >>>
> >>> OK, thanks for the clarification. This is a known problem. Have a look
> >>> at I think we consider that one to 0158115f702b ("memcg, kmem: deprecate
> >>> kmem.limit_in_bytes"). We are reporting the deprecated and to-be removed
> >>> status since 2019 without any actual report sugested by the kernel
> >>> message. Maybe we should try and remove it and see whether that prompts
> >>> some pushback.
> >>>
> >>
> >> Yes, I think now should be the right time to take the next step for
> >> deprecation of kmem limits:
> >> https://lore.kernel.org/all/20201118175726.2453120-1-shakeelb@google.com/
> >
> > Are you going to push it to stable kernels too?
>
> Btw CONFIG_MEMCG_KMEM=y is set both in RHEL8 kernels and in ubuntu 20.04 LTS kernel 5.11.0-37.
>

CONFIG_MEMCG_KMEM is orthogonal to setting kmem limits. We are not
disabling the kmem accounting.