Messages in this thread |  | | From | Joel Fernandes <> | Date | Wed, 24 Jan 2018 14:06:05 -0800 | Subject | Re: [PATCH v3 1/3] sched/fair: add util_est on top of PELT |
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On Wed, Jan 24, 2018 at 11:16 AM, Patrick Bellasi <patrick.bellasi@arm.com> wrote: > On 24-Jan 08:40, Joel Fernandes wrote: >> On Tue, Jan 23, 2018 at 10:08 AM, Patrick Bellasi >> <patrick.bellasi@arm.com> wrote: >> > The util_avg signal computed by PELT is too variable for some use-cases. >> > For example, a big task waking up after a long sleep period will have its >> > utilization almost completely decayed. This introduces some latency before >> > schedutil will be able to pick the best frequency to run a task. >> [...] >> > -static inline unsigned long task_util(struct task_struct *p); >> > static unsigned long cpu_util_wake(int cpu, struct task_struct *p); >> > >> > static unsigned long capacity_spare_wake(int cpu, struct task_struct *p) >> > @@ -6262,6 +6337,11 @@ static inline unsigned long task_util(struct task_struct *p) >> > return p->se.avg.util_avg; >> > } >> > >> > +static inline unsigned long task_util_est(struct task_struct *p) >> > +{ >> > + return max(p->se.avg.util_est.ewma, p->se.avg.util_est.last); >> > +} >> > + >> > /* >> > * cpu_util_wake: Compute cpu utilization with any contributions from >> > * the waking task p removed. >> > diff --git a/kernel/sched/features.h b/kernel/sched/features.h >> > index 9552fd5854bf..c459a4b61544 100644 >> > --- a/kernel/sched/features.h >> > +++ b/kernel/sched/features.h >> > @@ -85,3 +85,8 @@ SCHED_FEAT(ATTACH_AGE_LOAD, true) >> > SCHED_FEAT(WA_IDLE, true) >> > SCHED_FEAT(WA_WEIGHT, true) >> > SCHED_FEAT(WA_BIAS, true) >> > + >> > +/* >> > + * UtilEstimation. Use estimated CPU utilization. >> > + */ >> > +SCHED_FEAT(UTIL_EST, false) >> > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h >> > index 2e95505e23c6..0b4d9750a927 100644 >> > --- a/kernel/sched/sched.h >> > +++ b/kernel/sched/sched.h >> > @@ -470,6 +470,7 @@ struct cfs_rq { >> > * CFS load tracking >> > */ >> > struct sched_avg avg; >> > + unsigned long util_est_runnable; >> >> Since struct sched_avg would now have util_est, cfs_rq gets it too. >> Then can we not try to reuse that struct and avoid having to expand >> cfs_rq more than needed? > > Yes, that's possible now... the main issue is that for RQ's we do not > track an EWMA, but still we can use the util_est::last field or maybe > use a union just to use a better name when used from the RQ side.
Yes I think its good to make use of the space we're adding in cfs_rq that's not used for other things.
> >> I went through previous conversations and couldn't find a reason, if I >> missed something I appreciate if you can explain the rationale. > > I've used a separate filed just because SE's util_est was not part of > sched_avg, and missed the opportunity to consolidate better this now > that we moved it. Thanks for pointing this out ;-)
You're welcome :)
thanks,
- Joel
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