Re: [patch -mm 1/9 v2] oom: filter tasks not sharing the same cpuset

[Nick Piggin <npiggin@suse.de>]

On Mon, Feb 15, 2010 at 02:20:01PM -0800, David Rientjes wrote:
> Tasks that do not share the same set of allowed nodes with the task that
> triggered the oom should not be considered as candidates for oom kill.
> 
> Tasks in other cpusets with a disjoint set of mems would be unfairly
> penalized otherwise because of oom conditions elsewhere; an extreme
> example could unfairly kill all other applications on the system if a
> single task in a user's cpuset sets itself to OOM_DISABLE and then uses
> more memory than allowed.
> 
> Killing tasks outside of current's cpuset rarely would free memory for
> current anyway.
> 
> Acked-by: Rik van Riel <riel@redhat.com>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Signed-off-by: David Rientjes <rientjes@google.com>

Acked-by: Nick Piggin <npiggin@suse.de>

> ---
>  mm/oom_kill.c |   12 +++---------
>  1 files changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -35,7 +35,7 @@ static DEFINE_SPINLOCK(zone_scan_lock);
>  /* #define DEBUG */
>  
>  /*
> - * Is all threads of the target process nodes overlap ours?
> + * Do all threads of the target process overlap our allowed nodes?
>   */
>  static int has_intersects_mems_allowed(struct task_struct *tsk)
>  {
> @@ -167,14 +167,6 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
>  		points /= 4;
>  
>  	/*
> -	 * If p's nodes don't overlap ours, it may still help to kill p
> -	 * because p may have allocated or otherwise mapped memory on
> -	 * this node before. However it will be less likely.
> -	 */
> -	if (!has_intersects_mems_allowed(p))
> -		points /= 8;
> -
> -	/*
>  	 * Adjust the score by oom_adj.
>  	 */
>  	if (oom_adj) {
> @@ -266,6 +258,8 @@ static struct task_struct *select_bad_process(unsigned long *ppoints,
>  			continue;
>  		if (mem && !task_in_mem_cgroup(p, mem))
>  			continue;
> +		if (!has_intersects_mems_allowed(p))
> +			continue;
>  
>  		/*
>  		 * This task already has access to memory reserves and is