Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 2 Aug 2018 17:55:24 +0200 | Subject | Re: [PATCH v5 09/14] sched: Add over-utilization/tipping point indicator |
| |
On Thu, 2 Aug 2018 at 17:30, Quentin Perret <quentin.perret@arm.com> wrote: > > On Thursday 02 Aug 2018 at 17:14:15 (+0200), Vincent Guittot wrote: > > On Thu, 2 Aug 2018 at 16:14, Quentin Perret <quentin.perret@arm.com> wrote: > > > Good point, setting the util_avg to 0 for new tasks should help > > > filtering out those tiny tasks too. And that would match with the idea > > > of letting tasks build their history before looking at their util_avg ... > > > > > > But there is one difference w.r.t frequency selection. The current code > > > won't mark the system overutilized, but will let sugov raise the > > > frequency when a new task is enqueued. So in case of a fork bomb, we > > > > If the initial value of util_avg is 0, we should not have any impact > > on the util_avg of the cfs rq on which the task is attached, isn't it > > ? so this should not impact both the over utilization state and the > > frequency selected by sugov or I'm missing something ? > > What I tried to say is that setting util_avg to 0 for new tasks will > prevent schedutil from raising the frequency in case of a fork bomb, and > I think that could be an issue. And I think this isn't an issue with the > patch as-is ...
ok. So you also want to deal with fork bomb Not sure that you don't have some problem with current proposal too because select_task_rq_fair will always return prev_cpu because util_avg and util_est are 0 at that time
> > Sorry if that wasn't clear > > > Then, select_task_rq_fair is called for a new task but util_avg is > > still 0 at that time in the current code so you will have consistent > > util_avg of the new task before and after calling > > find_energy_efficient_cpu > > New tasks don't go in find_energy_efficient_cpu(), because, as you said, > they have no consistent util_avg yet when select_task_rq_fair() is called > for the first time. > > Thanks, > Quentin
| |