linux-kernel - Re: [PATCH 0/4] CPUFreq: Implement per policy instances of governors

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Date:	Tue, 5 Feb 2013 12:39:50 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>,
	Robin Randhawa <Robin.Randhawa@....com>,
	Steve Bannister <Steve.Bannister@....com>,
	Liviu Dudau <Liviu.Dudau@....com>
Subject: Re: [PATCH 0/4] CPUFreq: Implement per policy instances of governors

On Tue, Feb 05, 2013 at 11:29:04AM +0000, Charles Garcia-Tobin wrote:
> Actually shooting myself in the foot here, Krait is not such a great
> example because although you can use difference between frequencies
> you are less likely to use different tunables (not inconceivable
> but unlikely). The best examples systems are multi cluster and
> hereterogeneous systems, like the recently announced Samsung Exynos 5
> octa http://en.wikipedia.org/wiki/Exynos_(system_on_chip). We will see
> more systems like this appearing, sporting low power cores combined
> with high performance ones, all running at the same time. I appreciate
> this is all very new, but more will come, and the requirement to have
> different tunables per cluster is very real. In ARM on our own multi
> cluster test chip, using an experimental version of this approach, we
> have seen good improvements in power consumption without compromising
> performance.

Ok, thanks for giving this insight, this is useful.

Question: do you need the granularity of that control to be per cpu
(with that I mean what linux understands under "cpu," i.e. logical or
physical core) or does one governor suffice per a set of cores, or as
you call it, a cluster?

> (Apologies ahead for any bit my mail server appends, not much I can do
> about it)

Yeah, my condolences :-)

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Leaving it in, in case you haven't seen how it looks like :-)

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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