Messages in this thread | | | Date | Thu, 31 Oct 2019 16:56:57 +0000 | From | Qais Yousef <> | Subject | Re: [Patch v4 4/6] sched/fair: update cpu_capcity to reflect thermal pressure |
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On 10/31/19 12:03, Thara Gopinath wrote: > On 10/31/2019 06:53 AM, Qais Yousef wrote: > > On 10/28/19 16:30, Peter Zijlstra wrote: > >> On Wed, Oct 23, 2019 at 01:28:40PM +0100, Qais Yousef wrote: > >>> On 10/22/19 16:34, Thara Gopinath wrote: > >>>> cpu_capacity relflects the maximum available capacity of a cpu. Thermal > >>>> pressure on a cpu means this maximum available capacity is reduced. This > >>>> patch reduces the average thermal pressure for a cpu from its maximum > >>>> available capacity so that cpu_capacity reflects the actual > >>>> available capacity. > >>>> > >>>> Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org> > >>>> --- > >>>> kernel/sched/fair.c | 1 + > >>>> 1 file changed, 1 insertion(+) > >>>> > >>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > >>>> index 4f9c2cb..be3e802 100644 > >>>> --- a/kernel/sched/fair.c > >>>> +++ b/kernel/sched/fair.c > >>>> @@ -7727,6 +7727,7 @@ static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu) > >>>> > >>>> used = READ_ONCE(rq->avg_rt.util_avg); > >>>> used += READ_ONCE(rq->avg_dl.util_avg); > >>>> + used += READ_ONCE(rq->avg_thermal.load_avg); > >>> > >>> Maybe a naive question - but can we add util_avg with load_avg without > >>> a conversion? I thought the 2 signals have different properties. > >> > >> Changelog of patch #1 explains, it's in that dense blob of text. > >> > >> But yes, you're quite right that that wants a comment here. > > > > Thanks for the pointer! A comment would be nice indeed. > > > > To make sure I got this correctly - it's because avg_thermal.load_avg > > represents delta_capacity which is already a 'converted' form of load. So this > > makes avg_thermal.load_avg a util_avg really. Correct? > Hello Quais, > > Sorry for not replying to your earlier email. Thanks for the review. > So if you look at the code, util_sum in calculated as a binary signal > converted into capacity. Check out the the below snippet from accumulate_sum > > if (load) > sa->load_sum += load * contrib; > if (runnable) > sa->runnable_load_sum += runnable * contrib; > if (running) > sa->util_sum += contrib << SCHED_CAPACITY_SHIFT; > > So the actual delta for the thermal pressure will never be considered > if util_avg is used. > > I will update this patch with relevant comment.
Okay thanks for the explanation.
-- Qais Yousef
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