Messages in this thread | | | Date | Thu, 27 Jul 2017 12:49:51 +0530 | From | Viresh Kumar <> | Subject | Re: [Eas-dev] [PATCH V4 0/3] sched: cpufreq: Allow remote callbacks |
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On 26-07-17, 23:23, Joel Fernandes (Google) wrote: > Ok, but the "heavy" in init_entity_runnable_average means for load, > not the util_avg. The util_avg is what's used for frequency scaling > IIUC and is set to 0 in that function no?
That's because the task isn't enqueued yet and so don't have any utilization. The last line of that routine is a comment which says:
/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
But once the task is enqueued, this load_avg will get considered for sure :)
> > The application was written by Steve (all credit goes to him) before > > he left Linaro, but I did test it with ftrace. What I saw with ftrace > > was that the freq isn't reevaluated for almost an entire tick many > > times because we enqueued the task remotely. And that changes with > > this series. > > > >> > The reason being that this patchset only targets a corner case, where > >> > following are required to be true to improve performance and that > >> > doesn't happen too often with these tests: > >> > > >> > - Task is migrated to another CPU. > >> > - The task has maximum demand initially, and should take the CPU to > >> > >> Just to make the cover-letter more clear and also confirming with you > >> I understand the above usecase, maybe in the future this can reworded > >> from "initially" to "before the migration" and "take the CPU" to "take > >> the target CPU of the migration" ? > > > > I can reword it a bit, but the test case wasn't really migrating > > anything and was looking only at the initial loads. > > Ok, I wasn't talking about the synthetic test in the second part of my > email above but about the explanation you gave about Galleryfling > improvement (that the migration of a task with high utilization > doesn't update the target frequency) which makes sense to me so we are > on the same page about that.
Okay, great.
-- viresh
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