Messages in this thread | | | Date | Thu, 21 Jul 2022 15:24:47 +0100 | From | Qais Yousef <> | Subject | Re: [PATCH 7/7] sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition |
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On 07/20/22 15:39, Xuewen Yan wrote: > Hi Qais > > On Thu, Jun 30, 2022 at 3:48 AM Qais Yousef <qais.yousef@arm.com> wrote: > > > > If the utilization of the woken up task is 0, we skip the energy > > calculation because it has no impact. > > > > But if the task is boosted (uclamp_min != 0) will have an impact on task > > placement and frequency selection. Only skip if the util is truly > > 0 after applying uclamp values. > > > > Change uclamp_task_cpu() signature to avoid unnecessary additional calls > > to uclamp_eff_get(). feec() is the only user now. > > > > Fixes: 732cd75b8c920 ("sched/fair: Select an energy-efficient CPU on task wake-up") > > Signed-off-by: Qais Yousef <qais.yousef@arm.com> > > --- > > kernel/sched/fair.c | 14 ++++++++------ > > 1 file changed, 8 insertions(+), 6 deletions(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 499ef7a7288c..a112ca45864c 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -4057,14 +4057,16 @@ static inline unsigned long task_util_est(struct task_struct *p) > > } > > > > #ifdef CONFIG_UCLAMP_TASK > > -static inline unsigned long uclamp_task_util(struct task_struct *p) > > +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_eff_value(p, UCLAMP_MIN), > > - uclamp_eff_value(p, UCLAMP_MAX)); > > + return clamp(task_util_est(p), uclamp_min, uclamp_max); > > } > > #else > > -static inline unsigned long uclamp_task_util(struct task_struct *p) > > +static inline unsigned long uclamp_task_util(struct task_struct *p, > > + unsigned long uclamp_min, > > + unsigned long uclamp_max) > > { > > return task_util_est(p); > > } > > @@ -6913,7 +6915,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) > > target = prev_cpu; > > > > sync_entity_load_avg(&p->se); > > - if (!task_util_est(p)) > > + if (!uclamp_task_util(p, p_util_min, p_util_max)) > > Is it not enough to just replace the task_util_est with the > uclamp_task_util? If change the definition of uclamp_task_util, > that means it have to get task's uclamp first if user want to call the > function, may increase the code complex farther more?
Calling uclamp_eff_value() all the time is not cheap actually.
We can easily add two versions when we need to:
__uclamp_task_util(p, uclamp_min, uclamp_max);
uclamp_task_util(p) { uclamp_min = uclamp_eff_value(); uclamp_max = uclamp_eff_value(); return __uclamp_eff_value(p, uclamp_min, uclamp_max); }
When we need to. Since we have a single user now, there's no need to do this now and if we ever get more users it'd be easy to refactor then?
Thanks!
-- Qais Yousef
> > > goto unlock; > > > > for (; pd; pd = pd->next) { > > -- > > 2.25.1 > > > > BR > --- > xuewen.yan
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