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 <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Nitin Gupta <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
David Rientjes 2010-09-22 13:04:52 -07:00 • committed by Linus Torvalds
commit f19e8aa11a

View file

@ -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;
}