linux-kernel - Re: [RFC PATCH 06/16] arm: topology: Define TC2 sched energy and provide it to scheduler

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Message-ID: <20140607235307.GD22261@intel.com>
Date:	Sun, 8 Jun 2014 07:53:07 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Dirk Brandewie <dirk.brandewie@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Morten Rasmussen <morten.rasmussen@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	Dietmar Eggemann <Dietmar.Eggemann@....com>,
	len.brown@...el.com, jacob.jun.pan@...ux.intel.com
Subject: Re: [RFC PATCH 06/16] arm: topology: Define TC2 sched energy and
 provide it to scheduler

On Fri, Jun 06, 2014 at 02:13:05PM +0200, Ingo Molnar wrote:
> 
> Leakage current typically gets higher with higher frequencies, but 
> it's also highly process dependent AFAIK.
> 

In general, you can assume leakage power ~ V^2.

> If switching power dissipation is the main factor in power use, then 
> we can essentially assume that P ~ V^2, at the same frequency - and 
> scales linearly with frequency - but real work performed also scales 
> semi-linearly with frequency for many workloads, so that's an 
> invariant for everything except highly memory bound workloads.
> 

Agreed. Strictly, Energy ~ V^2.
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