linux-kernel - Re: [PATCH v3 3/4] sched: scheduler-driven cpu frequency selection

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Message-ID: <559ADFCE.3050103@arm.com>
Date:	Mon, 06 Jul 2015 21:06:38 +0100
From:	Dietmar Eggemann <dietmar.eggemann@....com>
To:	Michael Turquette <mturquette@...libre.com>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	"riel@...hat.com" <riel@...hat.com>,
	"efault@....de" <efault@....de>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	"amit.kucheria@...aro.org" <amit.kucheria@...aro.org>,
	Juri Lelli <Juri.Lelli@....com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
	"ashwin.chaugule@...aro.org" <ashwin.chaugule@...aro.org>,
	"alex.shi@...aro.org" <alex.shi@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"abelvesa@...il.com" <abelvesa@...il.com>,
	"pebolle@...cali.nl" <pebolle@...cali.nl>
Subject: Re: [PATCH v3 3/4] sched: scheduler-driven cpu frequency selection

Hi Mike,

On 27/06/15 00:53, Michael Turquette wrote:
> From: Michael Turquette <mturquette@...libre.com>
> 

[...]

>  comment "CPU frequency scaling drivers"
> 
>  config CPUFREQ_DT
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index 1f2c9a1..30241c9 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -494,6 +494,9 @@ extern struct cpufreq_governor cpufreq_gov_ondemand;
>  #elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE)
>  extern struct cpufreq_governor cpufreq_gov_conservative;
>  #define CPUFREQ_DEFAULT_GOVERNOR       (&cpufreq_gov_conservative)
> +#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_SCHED_GOV)
> +extern struct cpufreq_governor cpufreq_gov_sched_gov;

To get it building with CONFIG_CPU_FREQ_DEFAULT_GOV_SCHED=y .

-#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_SCHED_GOV)
-extern struct cpufreq_governor cpufreq_gov_sched_gov;
+#elif defined(CONFIG_CPU_FREQ_DEFAULT_GOV_SCHED)
+extern struct cpufreq_governor cpufreq_gov_sched;

> +#define CPUFREQ_DEFAULT_GOVERNOR       (&cpufreq_gov_sched)
>  #endif

> +
> +/**
> + * cpufreq_sched_set_capacity - interface to scheduler for changing capacity values

[...]

minor nit:

s/cpufreq_sched_set_capacity/cpufreq_sched_set_cap

> + * @cpu: cpu whose capacity utilization has recently changed
> + * @capacity: the new capacity requested by cpu
> + *
> + * cpufreq_sched_sched_capacity is an interface exposed to the scheduler so
> + * that the scheduler may inform the governor of updates to capacity
> + * utilization and make changes to cpu frequency. Currently this interface is
> + * designed around PELT values in CFS. It can be expanded to other scheduling
> + * classes in the future if needed.
> + *
> + * cpufreq_sched_set_capacity raises an IPI. The irq_work handler for that IPI
> + * wakes up the thread that does the actual work, cpufreq_sched_thread.
> + *
> + * This functions bails out early if either condition is true:
> + * 1) this cpu did not the new maximum capacity for its frequency domain
> + * 2) no change in cpu frequency is necessary to meet the new capacity request
> + */
> +void cpufreq_sched_set_cap(int cpu, unsigned long capacity)
> +{
> +       unsigned int freq_new, cpu_tmp;
> +       struct cpufreq_policy *policy;
> +       struct gov_data *gd;
> +       unsigned long capacity_max = 0;

[...]

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