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

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Message-ID: <YL5tBQ3utMzUkHF3@dhcp22.suse.cz>
Date:   Mon, 7 Jun 2021 21:01:25 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Aaron Tomlin <atomlin@...hat.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org, vbabka@...e.cz,
        llong@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] mm/oom_kill: allow oom kill allocating task for
 non-global case

On Mon 07-06-21 17:31:03, 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.

This is a global oom policy not a memcg specific one so a historical
behavior would change. So I do not think we can change that. The policy
can be implemented on the memcg level but this would require a much more
detailed explanation of the usecase and the semantic (e.g. wrt.
hierarchical behavior etc).
 
> 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;
> -- 
> 2.26.3

-- 
Michal Hocko
SUSE Labs