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SubjectRe: [PATCH v3] sched/cpufreq: optimize cpufreq update kicker to avoid update multiple times
From
Date
[Added linux-pm to the CC - can you please do so for PM-related patches 
in the future?]

On 4/22/2016 11:07 AM, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@hotmail.com>
>
> Sometimes delta_exec is 0 due to update_curr() is called multiple times,
> this is captured by:
>
> u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start;
>
> This patch optimizes the cpufreq update kicker by bailing out when nothing
> changed, it will benefit the upcoming schedutil, since otherwise it will
> (over)react to the special util/max combination.
>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>

The changelog looks better now, thanks!

Peter, do I think correctly that you're going to take care of this one?
Or do you want me to take it?

> ---
> v1 -> v2:
> * add From: head
> v2 -> v3:
> * update changelog
>
> kernel/sched/deadline.c | 8 ++++----
> kernel/sched/rt.c | 8 ++++----
> 2 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index affd97e..8f9b5af 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -717,10 +717,6 @@ static void update_curr_dl(struct rq *rq)
> if (!dl_task(curr) || !on_dl_rq(dl_se))
> return;
>
> - /* Kick cpufreq (see the comment in linux/cpufreq.h). */
> - if (cpu_of(rq) == smp_processor_id())
> - cpufreq_trigger_update(rq_clock(rq));
> -
> /*
> * Consumed budget is computed considering the time as
> * observed by schedulable tasks (excluding time spent
> @@ -736,6 +732,10 @@ static void update_curr_dl(struct rq *rq)
> return;
> }
>
> + /* kick cpufreq (see the comment in linux/cpufreq.h). */
> + if (cpu_of(rq) == smp_processor_id())
> + cpufreq_trigger_update(rq_clock(rq));
> +
> schedstat_set(curr->se.statistics.exec_max,
> max(curr->se.statistics.exec_max, delta_exec));
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index c41ea7a..19e1306 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -953,14 +953,14 @@ static void update_curr_rt(struct rq *rq)
> if (curr->sched_class != &rt_sched_class)
> return;
>
> - /* Kick cpufreq (see the comment in linux/cpufreq.h). */
> - if (cpu_of(rq) == smp_processor_id())
> - cpufreq_trigger_update(rq_clock(rq));
> -
> delta_exec = rq_clock_task(rq) - curr->se.exec_start;
> if (unlikely((s64)delta_exec <= 0))
> return;
>
> + /* Kick cpufreq (see the comment in linux/cpufreq.h). */
> + if (cpu_of(rq) == smp_processor_id())
> + cpufreq_trigger_update(rq_clock(rq));
> +
> schedstat_set(curr->se.statistics.exec_max,
> max(curr->se.statistics.exec_max, delta_exec));
>

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