Commit f19e8aa1 authored Sep 22, 2010 by David Rientjes Committed by Linus Torvalds Sep 22, 2010

oom: always return a badness score of non-zero for eligible tasks



A task's badness score is roughly a proportion of its rss and swap
compared to the system's capacity.  The scale ranges from 0 to 1000 with
the highest score chosen for kill.  Thus, this scale operates on a
resolution of 0.1% of RAM + swap.  Admin tasks are also given a 3% bonus,
so the badness score of an admin task using 3% of memory, for example,
would still be 0.

It's possible that an exceptionally large number of tasks will combine to
exhaust all resources but never have a single task that uses more than
0.1% of RAM and swap (or 3.0% for admin tasks).

This patch ensures that the badness score of any eligible task is never 0
so the machine doesn't unnecessarily panic because it cannot find a task
to kill.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 767b68e9

mm/oom_kill.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -208,8 +208,13 @@ unsigned int oom_badness(struct task_struct p, struct mem_cgroup mem,
		*/
		points += p->signal->oom_score_adj;

		if (points < 0)
		return 0;
		/*
		* Never return 0 for an eligible task that may be killed since it's
		* possible that no single user task uses more than 0.1% of memory and
		* no single admin tasks uses more than 3.0%.
		*/
		if (points <= 0)
		return 1;
		return (points < 1000) ? points : 1000;
		}

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