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From:   Waiman Long <llong@redhat.com>
Subject: Re: [RFC PATCH] mm/oom_kill: allow oom kill allocating task for
 non-global case
To:     Aaron Tomlin <atomlin@redhat.com>, linux-mm@kvack.org
Cc:     akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com,
        llong@redhat.com, linux-kernel@vger.kernel.org
References: <20210607163103.632681-1-atomlin@redhat.com>
Message-ID: <c16893a9-35e2-7625-d7f3-83488f874040@redhat.com>
Date:   Mon, 7 Jun 2021 12:42:54 -0400
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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@redhat.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. I don't see a reason why this should be limited to a global OOM only.

Acked-by: Waiman Long <longman@redhat.com>

Cheers,
Longman