The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: 68f7b5cc835de7d5b6c7696533c126018171e793
Gitweb: https://git.kernel.org/tip/68f7b5cc835de7d5b6c7696533c126018171e793
Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
AuthorDate: Wed, 24 Jun 2020 17:44:22 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 25 Jun 2020 13:45:38 +02:00
sched/cfs: change initial value of runnable_avg
Some performance regression on reaim benchmark have been raised with
commit 070f5e860ee2 ("sched/fair: Take into account runnable_avg to classify group")
The problem comes from the init value of runnable_avg which is initialized
with max value. This can be a problem if the newly forked task is finally
a short task because the group of CPUs is wrongly set to overloaded and
tasks are pulled less agressively.
Set initial value of runnable_avg equals to util_avg to reflect that there
is no waiting time so far.
Fixes: 070f5e860ee2 ("sched/fair: Take into account runnable_avg to classify group")
Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx>
Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200624154422.29166-1-vincent.guittot@xxxxxxxxxx
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index cbcb2f7..658aa7a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -806,7 +806,7 @@ void post_init_entity_util_avg(struct task_struct *p)
}
}
- sa->runnable_avg = cpu_scale;
+ sa->runnable_avg = sa->util_avg;
if (p->sched_class != &fair_sched_class) {
/*
|