linux-kernel - Re: [PATCH v5 06/12] sched: add per rq cpu_capacity

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Message-ID: <CAKfTPtAmUe3GUL51Ow24pVq4Q2pMKJO5A7wG1Mic+akg=ozkjg@mail.gmail.com>
Date:	Wed, 10 Sep 2014 16:19:56 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	Rik van Riel <riel@...hat.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Mike Galbraith <efault@....de>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v5 06/12] sched: add per rq cpu_capacity_orig

On 10 September 2014 15:53, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, Aug 26, 2014 at 01:06:49PM +0200, Vincent Guittot wrote:
>> This new field cpu_capacity_orig reflects the available capacity of a CPUs
>> unlike the cpu_capacity which reflects the current capacity that can be altered
>> by frequency and rt tasks.
>>
>
> No real objection to the patch as such, but the Changelog fails to tell
> us why you want this.

the cpu_capacity_orig  is used in several places in the following
patches to detect when a CPU's capacity has been noticeably reduced so
we can trig load balance to look for a CPU with full capacity.
As an example, we can detect when a CPU handles a significant amount
of irq (with CONFIG_IRQ_TIME_ACCOUNTING) but is seen as an idle CPU by
scheduler whereas really idle CPU are available
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