From: Vincent Guittot vincent.guittot@linaro.org
[ 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@intel.com Signed-off-by: Vincent Guittot vincent.guittot@linaro.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20200624154422.29166-1-vincent.guittot@linaro.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 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) { /*