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

From: Nick Piggin
Date: Tue Feb 16 2010 - 01:14:48 EST


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@xxxxxxxxxx>
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>

Acked-by: Nick Piggin <npiggin@xxxxxxx>

> ---
> 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
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