Messages in this thread | | | Subject | Re: [PATCH] sched/cfs: change initial value of runnable_avg | From | Holger Hoffstätte <> | Date | Thu, 25 Jun 2020 11:24:28 +0200 |
| |
On 2020-06-24 17:44, Vincent Guittot wrote: > 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> > --- > 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 0424a0af5f87..45e467bf42fc 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) { > /* >
Something is wrong here. I woke up my machine from suspend-to-RAM this morning and saw that a completely idle machine had a loadavg of ~7. According to my monitoring system this happened to be the loadavg right before I suspended. I've reverted this, rebooted, created a loadavg >0, suspended and after wake up loadavg again correctly ranges between 0 and whatever, as expected.
-h
| |