Messages in this thread | | | Date | Fri, 26 Apr 2024 11:16:23 +0100 | Subject | Re: [RFC][PATCH 08/10] sched/fair: Implement delayed dequeue | From | Luis Machado <> |
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On 4/26/24 10:32, Peter Zijlstra wrote: > On Thu, Apr 25, 2024 at 01:49:49PM +0200, Peter Zijlstra wrote: >> On Thu, Apr 25, 2024 at 12:42:20PM +0200, Peter Zijlstra wrote: >> >>>> I wonder if the delayed dequeue logic is having an unwanted effect on the calculation of >>>> utilization/load of the runqueue and, as a consequence, we're scheduling things to run on >>>> higher OPP's in the big cores, leading to poor decisions for energy efficiency. >>> >>> Notably util_est_update() gets delayed. Given we don't actually do an >>> enqueue when a delayed task gets woken, it didn't seem to make sense to >>> update that sooner. >> >> The PELT runnable values will be inflated because of delayed dequeue. >> cpu_util() uses those in the @boost case, and as such this can indeed >> affect things. >> >> This can also slightly affect the cgroup case, but since the delay goes >> away as contention goes away, and the cgroup case must already assume >> worst case overlap, this seems limited. >> >> /me goes ponder things moar. > > First order approximation of a fix would be something like the totally > untested below I suppose...
Thanks Peter. Let me give it a try and I'll report back.
> > --- > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index cfd1fd188d29..f3f70b5adca0 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5391,6 +5391,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) > if (cfs_rq->next == se) > cfs_rq->next = NULL; > se->sched_delayed = 1; > + update_load_avg(cfs_rq, se, 0); > return false; > } > } > @@ -6817,6 +6818,7 @@ requeue_delayed_entity(struct sched_entity *se) > } > > se->sched_delayed = 0; > + update_load_avg(qcfs_rq, se, 0); > } > > /* > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index d07a3b98f1fb..d16529613123 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -810,6 +810,9 @@ static inline void se_update_runnable(struct sched_entity *se) > > static inline long se_runnable(struct sched_entity *se) > { > + if (se->sched_delayed) > + return false; > + > if (entity_is_task(se)) > return !!se->on_rq; > else > @@ -823,6 +826,9 @@ static inline void se_update_runnable(struct sched_entity *se) {} > > static inline long se_runnable(struct sched_entity *se) > { > + if (se->sched_delayed) > + return false; > + > return !!se->on_rq; > } > #endif
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