Re: [PATCH] oom: break after selecting process to kill

[Zhang Zhen <zhenzhang.zhang@huawei.com>]

On 2014/9/12 5:33, Niv Yehezkel wrote:
> There is no need to fallback and continue computing
> badness for each running process after we have found a
> process currently performing the swapoff syscall. We ought to
> immediately select this process for killing.
> 
> Signed-off-by: Niv Yehezkel <executerx@gmail.com>
> ---
>  mm/oom_kill.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 1e11df8..68ac30e 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -305,6 +305,7 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
>  	struct task_struct *g, *p;
>  	struct task_struct *chosen = NULL;
>  	unsigned long chosen_points = 0;
> +	bool process_selected = false;
>  
>  	rcu_read_lock();
>  	for_each_process_thread(g, p) {
> @@ -315,7 +316,8 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
>  		case OOM_SCAN_SELECT:
>  			chosen = p;
>  			chosen_points = ULONG_MAX;
> -			/* fall through */
> +			process_selected = true;
> +			break;
>  		case OOM_SCAN_CONTINUE:
>  			continue;
>  		case OOM_SCAN_ABORT:
> @@ -324,6 +326,8 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
>  		case OOM_SCAN_OK:
>  			break;
>  		};
> +		if (process_selected)
> +			break;

Hi,
The following comment shows that we prefer thread group leaders for display purposes.
If we break here and two threads in a thread group are performing the swapoff syscall, maybe we can not get thread
group leaders.

Thanks!

>  		points = oom_badness(p, NULL, nodemask, totalpages);
>  		if (!points || points < chosen_points)
>  			continue;
> 


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