linux-kernel - Re: [PATCH] mm/oom_kill: break evaluation when a task has been selected

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Date:   Wed, 1 Jun 2022 09:45:26 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Zhaoyu Liu <zackary.liu.pro@...il.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/oom_kill: break evaluation when a task has been
 selected

On Sat 14-05-22 15:52:28, Zhaoyu Liu wrote:
> oom points no longer need to be calculated if a task is oom_task_origin(),
> so return 1 to stop the oom_evaluate_task().

This doesn't really explain why this is really desired. Is this a fix,
optimization?

Please also note that this change has some side effects. For one, the
task marked as oom origin will get killed even if there is still a
pending oom victim which hasn't been fully dismantled. Is this
intentional?

> Signed-off-by: Zhaoyu Liu <zackary.liu.pro@...il.com>
> ---
>  mm/oom_kill.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 3996301450e8..b407fba21d19 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -308,7 +308,7 @@ static enum oom_constraint constrained_alloc(struct oom_control *oc)
>  static int oom_evaluate_task(struct task_struct *task, void *arg)
>  {
>  	struct oom_control *oc = arg;
> -	long points;
> +	long points = 0;
>  
>  	if (oom_unkillable_task(task))
>  		goto next;
> @@ -349,7 +349,7 @@ static int oom_evaluate_task(struct task_struct *task, void *arg)
>  	oc->chosen = task;
>  	oc->chosen_points = points;
>  next:
> -	return 0;
> +	return points == LONG_MAX;
>  abort:
>  	if (oc->chosen)
>  		put_task_struct(oc->chosen);
> -- 
> 2.17.1

-- 
Michal Hocko
SUSE Labs