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sched/cfs: change initial value of runnable_avg

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Some performance regression on reaim benchmark have been raised with
  commit 070f5e860e ("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: 070f5e860e ("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
This commit is contained in:
Vincent Guittot 2020-06-24 17:44:22 +02:00 committed by Borislav Petkov
parent 8c4890d1c3
commit e21cf43406
1 changed files with 1 additions and 1 deletions
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2
kernel/sched/fair.c
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@ -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) {
/*