linux-kernel - Re: [PATCH RFC v2 4/4] sched: cpufreq_cfs: pelt-based cpu frequency scaling

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Date:	Wed, 13 May 2015 11:19:23 +0200
From:	Paul Bolle <pebolle@...cali.nl>
To:	Michael Turquette <mturquette@...aro.org>
Cc:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	preeti@...ux.vnet.ibm.com, Morten.Rasmussen@....com,
	riel@...hat.com, efault@....de, nicolas.pitre@...aro.org,
	daniel.lezcano@...aro.org, dietmar.eggemann@....com,
	vincent.guittot@...aro.org, amit.kucheria@...aro.org,
	juri.lelli@....com, rjw@...ysocki.net, viresh.kumar@...aro.org,
	ashwin.chaugule@...aro.org, alex.shi@...aro.org, abelvesa@...il.com
Subject: Re: [PATCH RFC v2 4/4] sched: cpufreq_cfs: pelt-based cpu frequency
 scaling

One nit and one question follow.

>--- a/drivers/cpufreq/Kconfig
> +++ b/drivers/cpufreq/Kconfig

> +config CPU_FREQ_DEFAULT_GOV_CFS
> +	bool "cfs"
> +	select CPU_FREQ_GOV_CFS
> +	select CPU_FREQ_GOV_PERFORMANCE
> +	help
> +	  Use the CPUfreq governor 'cfs' as default. This scales
> +	  cpu frequency from the scheduler as per-entity load tracking
> +	  statistics are updated.

> +config CPU_FREQ_GOV_CFS
> +	tristate "'cfs' cpufreq governor"
> +	depends on CPU_FREQ
> +	select CPU_FREQ_GOV_COMMON
> +	help
> +	  'cfs' - this governor scales cpu frequency from the
> +	  scheduler as a function of cpu capacity utilization. It does
> +	  not evaluate utilization on a periodic basis (as ondemand
> +	  does) but instead is invoked from the completely fair
> +	  scheduler when updating per-entity load tracking statistics.
> +	  Latency to respond to changes in load is improved over polling
> +	  governors due to its event-driven design.
> +
> +	  If in doubt, say N.

> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -485,6 +485,9 @@ 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_CAP_GOV)
> +extern struct cpufreq_governor cpufreq_gov_cap_gov;
> +#define CPUFREQ_DEFAULT_GOVERNOR	(&cpufreq_gov_cap_gov)
>  #endif

Question: grepping for CPU_FREQ_DEFAULT_GOV_CAP_GOV and
cpufreq_gov_cap_gov didn't gave me hits in next-20150513. And this
series doesn't add them, does it? So where do they com from?

(Since you add CPU_FREQ_DEFAULT_GOV_CFS and cpufreq_cfs in this patch it
seems you intended to add those. I briefly looked into the way
CPUFREQ_DEFAULT_GOVERNOR is set in cpufreq.h when v1 came along, found
it to complicated for me, and promptly forgot the details, so please
double check.)
 
> --- a/kernel/sched/Makefile
> +++ b/kernel/sched/Makefile

> +obj-$(CONFIG_CPU_FREQ_GOV_CFS) += cpufreq_cfs.o

> --- /dev/null
> +++ b/kernel/sched/cpufreq_cfs.c

> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.

This states the license is GPL v2.

> +MODULE_LICENSE("GPL");

And, according to include/linux/module.h, this states the license is GPL
v2 or later. So I think that either the comment at the top of this file
or the ident used in the MODULE_LICENSE() macro needs to be changed.

Thanks,


Paul Bolle

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