linux-kernel - Re: [RFCv2 PATCH 00/23] sched: Energy cost model for energy-aware scheduling

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Date:	Mon, 7 Jul 2014 03:05:23 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"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>,
	"pjt@...gle.com" <pjt@...gle.com>
Subject: Re: [RFCv2 PATCH 00/23] sched: Energy cost model for energy-aware
 scheduling

Hi Morten,

Thanks, got it. Then another question,

On Fri, Jul 04, 2014 at 12:06:13PM +0100, Morten Rasmussen wrote:
> The patch set essentially puts tasks where it is most energy-efficient
> guided by the platform energy model. That should benefit any platform,
> SMP and big.LITTLE. That is at least the goal.
> 

I understand energy_diff_* functions are based on the energy model (though I
have not dived into the detail of how you change load balancing based on
energy_diff_*).

Speaking of the engergy model, I am not sure why elaborate "imprecise" energy
numbers do a better job than only a general statement: higher freq, more cap,
and more power.

Even for big.LITTLE systems, big and little CPUs also follow that statement
respectively. Then it is just a matter of where to place tasks between them.
Under such, the energy model might be useful, but still probably cpu_power_orig
(from Vincent) might be enough.

Thanks,
Yuyang
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