linux-kernel - Re: [RFC PATCH] mm/oom_kill: allow oom kill allocating task for non-global case

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Date:   Mon, 7 Jun 2021 11:43:19 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Waiman Long <llong@...hat.com>
Cc:     Aaron Tomlin <atomlin@...hat.com>, Linux MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] mm/oom_kill: allow oom kill allocating task for
 non-global case

On Mon, Jun 7, 2021 at 9:45 AM Waiman Long <llong@...hat.com> wrote:
>
> On 6/7/21 12:31 PM, Aaron Tomlin wrote:
> > At the present time, in the context of memcg OOM, even when
> > sysctl_oom_kill_allocating_task is enabled/or set, the "allocating"
> > task cannot be selected, as a target for the OOM killer.
> >
> > This patch removes the restriction entirely.
> >
> > Signed-off-by: Aaron Tomlin <atomlin@...hat.com>
> > ---
> >   mm/oom_kill.c | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > index eefd3f5fde46..3bae33e2d9c2 100644
> > --- a/mm/oom_kill.c
> > +++ b/mm/oom_kill.c
> > @@ -1089,9 +1089,9 @@ bool out_of_memory(struct oom_control *oc)
> >               oc->nodemask = NULL;
> >       check_panic_on_oom(oc);
> >
> > -     if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
> > -         current->mm && !oom_unkillable_task(current) &&
> > -         oom_cpuset_eligible(current, oc) &&
> > +     if (sysctl_oom_kill_allocating_task && current->mm &&
> > +            !oom_unkillable_task(current) &&
> > +            oom_cpuset_eligible(current, oc) &&
> >           current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
> >               get_task_struct(current);
> >               oc->chosen = current;
>
> To provide more context for this patch, we are actually seeing that in a
> customer report about OOM happened in a container where the dominating
> task used up most of the memory and it happened to be the task that
> triggered the OOM with the result that no killable process could be
> found.

Why was there no killable process? What about the process allocating
the memory or is this remote memcg charging?

> I don't see a reason why this should be limited to a global OOM only.
>
> Acked-by: Waiman Long <longman@...hat.com>
>
> Cheers,
> Longman
>