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oom: avoid killing a task if a thread sharing its mm cannot be killed 

The oom killer's goal is to kill a memory-hogging task so that it may
exit, free its memory, and allow the current context to allocate the
memory that triggered it in the first place.  Thus, killing a task is
pointless if other threads sharing its mm cannot be killed because of its
/proc/pid/oom_adj or /proc/pid/oom_score_adj value.

This patch checks whether any other thread sharing p->mm has an
oom_score_adj of OOM_SCORE_ADJ_MIN.  If so, the thread cannot be killed
and oom_badness(p) returns 0, meaning it's unkillable.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes 2010-10-26 14:21:23 -07:00 committed by Linus Torvalds
parent 3d5992d2ac
commit e18641e19a
1 changed files with 5 additions and 4 deletions
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9
mm/oom_kill.c
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@ -162,10 +162,11 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
return 0;
/*
* Shortcut check for OOM_SCORE_ADJ_MIN so the entire heuristic doesn't
* need to be executed for something that cannot be killed.
* Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN
* so the entire heuristic doesn't need to be executed for something
* that cannot be killed.
*/
if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
if (atomic_read(&p->mm->oom_disable_count)) {
task_unlock(p);
return 0;
}
@ -680,7 +681,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
read_lock(&tasklist_lock);
if (sysctl_oom_kill_allocating_task &&
!oom_unkillable_task(current, NULL, nodemask) &&
(current->signal->oom_adj != OOM_DISABLE)) {
current->mm && !atomic_read(&current->mm->oom_disable_count)) {
/*
* oom_kill_process() needs tasklist_lock held. If it returns
* non-zero, current could not be killed so we must fallback to