[PATCH 2/2] mm: oom: terminate the oom_evaluate_task() loop early

[Peng Zhang <zhangpeng362@huawei.com>]

From: ZhangPeng <zhangpeng362@huawei.com>

If task is allocating a lot of memory and has been marked to be killed
first, then it gets the highest score (LONG_MAX). Therefore, there is no
need to continue to calculate the points of other tasks. Just terminate
the oom_evaluate_task() loop early, when the task with the highest score
is found. By doing this, we can get some performance gains in
select_bad_process().
To implement it, the return value of oom_evaluate_task() is modified.
When the task with the highest score is found (points == LONG_MAX),
oom_evaluate_task() will return 1 and the loop will terminate early.

Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
---
 mm/oom_kill.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 10f7826c4035..02d11ae043aa 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -346,6 +346,8 @@ static int oom_evaluate_task(struct task_struct *task, void *arg)
 	get_task_struct(task);
 	oc->chosen = task;
 	oc->chosen_points = points;
+	if (points == LONG_MAX)
+		return 1;
 next:
 	return 0;
 abort:
-- 
2.25.1