2016-04-22 09:08:04

by Wanpeng Li

Subject: [PATCH v3] sched/cpufreq: optimize cpufreq update kicker to avoid update multiple times

From: Wanpeng Li <[email protected]>

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 <[email protected]>
---
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));

--
1.9.1

2016-04-22 12:05:10

by Wysocki, Rafael J

Subject: Re: [PATCH v3] sched/cpufreq: optimize cpufreq update kicker to avoid update multiple times

[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 <[email protected]>
>
> 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 <[email protected]>

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));
>

2016-04-25 14:31:41

by Peter Zijlstra

Subject: Re: [PATCH v3] sched/cpufreq: optimize cpufreq update kicker to avoid update multiple times

On Fri, Apr 22, 2016 at 02:04:56PM +0200, Rafael J. Wysocki wrote:
> [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 <[email protected]>
> >
> >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 <[email protected]>
>
> 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?

YEah, looks fine. I'll take it.

Thanks!

2016-04-28 10:27:21

by tip-bot for Vasyl Gomonovych

Subject: [tip:sched/core] sched/cpufreq: Optimize cpufreq update kicker to avoid update multiple times

Commit-ID: 594dd290cf5403a9a5818619dfff42d8e8e0518e
Gitweb: http://git.kernel.org/tip/594dd290cf5403a9a5818619dfff42d8e8e0518e
Author: Wanpeng Li <[email protected]>
AuthorDate: Fri, 22 Apr 2016 17:07:24 +0800
Committer: Ingo Molnar <[email protected]>
CommitDate: Thu, 28 Apr 2016 10:39:54 +0200

sched/cpufreq: Optimize cpufreq update kicker to avoid update multiple times

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 <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
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));