This is a note to let you know that I've just added the patch titled sched/cfs: change initial value of runnable_avg to the 5.7-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sched-cfs-change-initial-value-of-runnable_avg.patch and it can be found in the queue-5.7 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 9712223694fbc433231c75b3da4cf72ce9a76af9 Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Date: Wed Jun 24 17:44:22 2020 +0200 sched/cfs: change initial value of runnable_avg [ Upstream commit e21cf43406a190adfcc4bfe592768066fb3aaa9b ] 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 Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2ae7e30ccb33c..5725199b32dcf 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -807,7 +807,7 @@ 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) { /*