linux-kernel - Re: [PATCH 6/6] sched: final power vs capacity cleanup

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Date:	Thu, 15 May 2014 09:29:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH 6/6] sched: final power vs capacity cleanup

On Wed, May 14, 2014 at 04:57:10PM -0400, Nicolas Pitre wrote:
> It is better not to think about compute capacity as being equivalent to
> "CPU power".  The upcoming "power aware" scheduler may create confusion
> with the notion of energy consumption if "power" is used too liberally.
> 
> This contains the architecture visible changes.  Incidentally, only ARM
> takes advantage of the available pow^H^H^Hcapacity scaling hooks and
> therefore those changes outside kernel/sched/ are confined to one ARM
> specific file.  The default arch_scale_smt_power() hook is not overridden
> by anyone.
> 
> Replacements are as follows:
> 
> 	arch_scale_freq_power  --> arch_scale_freq_capacity
> 	arch_scale_smt_power   --> arch_scale_smt_capacity
> 	SCHED_POWER_SCALE      --> SCHED_CAPA_SCALE
> 	SCHED_POWER_SHIFT      --> SCHED_POWER_SHIFT

The patch seems to actually make that CAPA_SHIFT

> The local usage of "power" in arch/arm/kernel/topology.c is also changed
> to "capacity" as appropriate.

For some reason every time I read: 'capa' I think of some south American
monster -- http://en.wikipedia.org/wiki/Chupacabra, I'm not at all sure
why my brain links them.

But yes, once we kill the capacity stuff we have now with some
utilization bound, capacity becomes uniquely the compute capacity.

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