linux-kernel - RE: [patch 2/2] x86: Manage ENERGY_PERF_BIAS based on cpufreq governor

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Date:	Thu, 4 Mar 2010 15:34:33 -0800
From:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To:	Dave Jones <davej@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, H Peter Anvin <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Len Brown <lenb@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...il.com>
Subject: RE: [patch 2/2] x86: Manage ENERGY_PERF_BIAS based on cpufreq
 governor - v2

 

>-----Original Message-----
>From: Dave Jones [mailto:davej@...hat.com] 
>Sent: Thursday, March 04, 2010 3:28 PM
>To: Pallipadi, Venkatesh
>Cc: Ingo Molnar; H Peter Anvin; Thomas Gleixner; Len Brown; 
>linux-kernel@...r.kernel.org; linux-acpi@...r.kernel.org; 
>Venkatesh Pallipadi
>Subject: Re: [patch 2/2] x86: Manage ENERGY_PERF_BIAS based on 
>cpufreq governor - v2
>
>On Thu, Mar 04, 2010 at 03:14:56PM -0800, Venki Pallipadi wrote:
> 
> > +	if (!strncmp(gov->name, "performance", strlen("performance")))
> > +		epb_val = ENERGY_PERF_BIAS_PERF;
> > +	else if (!strncmp(gov->name, "powersave", strlen("powersave")))
> > +		epb_val = ENERGY_PERF_BIAS_POWER;
> > +	else
> > +		epb_val = ENERGY_PERF_BIAS_ONDEMAND;
> > +
> > +	set_epb_on_cpu(epb_val, cpu);
> > +	return 0;
>
>hardcoding a list of cpufreq governors is kinda icky, but I don't have
>a better solution.  We'll just have to be mindful of it if we ever
>get around to finally making performance/powersave personalities
>of ondemand as was discussed years ago.

Yes. In that case we will have to find some other way to tie this to
user preference.

>
>What if the governor is set to 'userspace' ?
>powernowd/cpufreqd are sort of ondemand-done-in-userspace, but there
>may also be other userspace governors we don't know about.
>I suppose it's not catastrophic..
>

Userspace/ondemand/conservative can all be at middle ground here as
they are mostly used where user expects adaptive kind of behaviour.

I did think about exporting this as a new tunable in /sys and let
userspace deal with it. But, that doesn't help with having sane default
values and users (background apps) may shoot themselves in the foot
with it.

Thanks,
Venki--
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