For systems with high CONFIG_NODES_SHIFT, checking nodes_intersect() for
each thread's set of allowed nodes is very expensive. It's unnecessary
to do this twice for each thread, once in select_bad_process() and once
in oom_badness(). We've already filtered unkillable threads at the point
where oom_badness() is called.
oom_badness() must still check if a thread is a kthread, however, to
ensure /proc/pid/oom_score doesn't report one as killable.
This significantly speeds up the tasklist iteration when there are a
large number of threads on the system and CONFIG_NODES_SHIFT is high.
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
mm/oom_kill.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -151,13 +151,16 @@ struct task_struct *find_lock_task_mm(struct task_struct *p)
return NULL;
}
+static bool is_unkillable_kthread(struct task_struct *p)
+{
+ return is_global_init(p) || (p->flags & PF_KTHREAD);
+}
+
/* return true if the task is not adequate as candidate victim task. */
static bool oom_unkillable_task(struct task_struct *p,
const struct mem_cgroup *memcg, const nodemask_t *nodemask)
{
- if (is_global_init(p))
- return true;
- if (p->flags & PF_KTHREAD)
+ if (is_unkillable_kthread(p))
return true;
/* When mem_cgroup_out_of_memory() and p is not member of the group */
@@ -185,7 +188,7 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
{
long points;
- if (oom_unkillable_task(p, memcg, nodemask))
+ if (is_unkillable_kthread(p))
return 0;
p = find_lock_task_mm(p);
@@ -478,9 +481,8 @@ static void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
if (child->mm == p->mm)
continue;
- /*
- * oom_badness() returns 0 if the thread is unkillable
- */
+ if (oom_unkillable_task(child, memcg, nodemask))
+ continue;
child_points = oom_badness(child, memcg, nodemask,
totalpages);
if (child_points > victim_points) {
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>