linux-kernel - Re: [PATCH v9 03/10] sched: remove frequency scaling from cpu

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Message-ID: <20141121123526.GD23177@e105550-lin.cambridge.arm.com>
Date:	Fri, 21 Nov 2014 12:35:26 +0000
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	"peterz@...radead.org" <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	"kamalesh@...ux.vnet.ibm.com" <kamalesh@...ux.vnet.ibm.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"riel@...hat.com" <riel@...hat.com>,
	"efault@....de" <efault@....de>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>
Subject: Re: [PATCH v9 03/10] sched: remove frequency scaling from
 cpu_capacity

On Mon, Nov 03, 2014 at 04:54:40PM +0000, Vincent Guittot wrote:
> Now that arch_scale_cpu_capacity has been introduced to scale the original
> capacity, the arch_scale_freq_capacity is no longer used (it was
> previously used by ARM arch). Remove arch_scale_freq_capacity from the
> computation of cpu_capacity. The frequency invariance will be handled in the
> load tracking and not in the CPU capacity. 

Just a note:

Yes, we are scaling the load tracking of each task to compensate for
frequency scaling. I think that is all fine. Later we will have to feed
the current frequency into the energy model as well to figure out if
putting more tasks on a cpu will/should cause the frequency to increase
or not. We don't need it for now and don't need to add it in the commit
message. It is just a reminder that we may actually want to use
arch_scale_freq_capacity() combined with cpu_capacity to provide this
input to the energy model later.
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