Messages in this thread | | | Subject | Re: [PATCH 2/2] sched/fair: Avoid calling sync_entity_load_avg() unnecessarily | From | Dietmar Eggemann <> | Date | Fri, 27 Apr 2018 10:30:39 +0200 |
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Hi Viresh,
On 04/26/2018 12:30 PM, Viresh Kumar wrote: > Call sync_entity_load_avg() directly from find_idlest_cpu() instead of > select_task_rq_fair(), as that's where we need to use task's utilization > value. And call sync_entity_load_avg() only after making sure sched > domain spans over one of the allowed CPUs for the task. > > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
The patch looks correct to me but we want to have the waking task synced against its previous rq also for EAS, i.e. for find_energy_efficient_cpu() which will sit next to find_idlest_cpu().
https://marc.info/?l=linux-kernel&m=152302907327168&w=2
The comment on top of the if condition would have to be changed though.
I would suggest we leave the call to sync_entity_load_avg() in the slow path of strf() so that we're not forced to call it in find_energy_efficient_cpu().
> --- > kernel/sched/fair.c | 16 +++++++--------- > 1 file changed, 7 insertions(+), 9 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 84fc74ddbd4b..5b1b4f91f132 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6199,6 +6199,13 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p > if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed)) > return prev_cpu; > > + /* > + * We need task's util for capacity_spare_wake, sync it up to prev_cpu's > + * last_update_time. > + */ > + if (!(sd_flag & SD_BALANCE_FORK)) > + sync_entity_load_avg(&p->se); > + > while (sd) { > struct sched_group *group; > struct sched_domain *tmp; > @@ -6651,15 +6658,6 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f > > if (unlikely(sd)) { > /* Slow path */ > - > - /* > - * We're going to need the task's util for capacity_spare_wake > - * in find_idlest_group. Sync it up to prev_cpu's > - * last_update_time. > - */ > - if (!(sd_flag & SD_BALANCE_FORK)) > - sync_entity_load_avg(&p->se); > - > new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag); > } else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */ > /* Fast path */ >
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