Messages in this thread Patch in this message | | | Date | Wed, 23 Aug 2023 12:30:17 +0200 | Subject | Re: [PATCH v4 2/3] sched/uclamp: Ignore (util == 0) optimization in feec() when p_util_max = 0 | From | Dietmar Eggemann <> |
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On 22/08/2023 00:45, Qais Yousef wrote: > find_energy_efficient_cpu() bails out early if effective util of the > task is 0 as the delta at this point will be zero and there's nothing > for EAS to do. When uclamp is being used, this could lead to wrong > decisions when uclamp_max is set to 0. In this case the task is capped
Does uclamp_max plays a role here? We check util and uclamp_min in this condition.
> to performance point 0, but it is actually running and consuming energy > and we can benefit from EAS energy calculations. > > Rework the condition so that it bails out for when util is actually 0 or > uclamp_min is requesting a higher performance point.
I do get the condition:
> + if (!task_util_est(p) && p_util_min == 0) > goto unlock;
which is !(task_util_est(p) || p_util_min)
But the text then should be '... bails out for when util is actually 0 and uclamp_min is 0 too'? Or 'uclamp_min is not requesting ...'.
> We can do that without needing to use uclamp_task_util(); remove it. > > Fixes: d81304bc6193 ("sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition") > Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> > Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> > --- > kernel/sched/fair.c | 18 +----------------- > 1 file changed, 1 insertion(+), 17 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 5da6538ed220..e19a36e7b433 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4571,22 +4571,6 @@ static inline unsigned long task_util_est(struct task_struct *p) > return max(task_util(p), _task_util_est(p)); > } > > -#ifdef CONFIG_UCLAMP_TASK > -static inline unsigned long uclamp_task_util(struct task_struct *p, > - unsigned long uclamp_min, > - unsigned long uclamp_max) > -{ > - return clamp(task_util_est(p), uclamp_min, uclamp_max); > -} > -#else > -static inline unsigned long uclamp_task_util(struct task_struct *p, > - unsigned long uclamp_min, > - unsigned long uclamp_max) > -{ > - return task_util_est(p); > -} > -#endif > - > static inline void util_est_enqueue(struct cfs_rq *cfs_rq, > struct task_struct *p) > { > @@ -7699,7 +7683,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) > target = prev_cpu; > > sync_entity_load_avg(&p->se); > - if (!uclamp_task_util(p, p_util_min, p_util_max)) > + if (!task_util_est(p) && p_util_min == 0) > goto unlock; > > eenv_task_busy_time(&eenv, p, prev_cpu);
With the question about the content of the patch header in mind:
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
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