linux-kernel - Re: [PATCH 1/7] sched: Introduce scale-invariant load tracking

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Date:	Fri, 10 Oct 2014 11:07:43 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	Morten Rasmussen <morten.rasmussen@....com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Dietmar Eggemann <Dietmar.Eggemann@....com>,
	Paul Turner <pjt@...gle.com>,
	Benjamin Segall <bsegall@...gle.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Mike Turquette <mturquette@...aro.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/7] sched: Introduce scale-invariant load tracking

On Wed, Oct 08, 2014 at 01:38:40PM +0200, Vincent Guittot wrote:
> I have in mind some system where the max achievable freq of a core
> depends of how many cores are running simultaneously because of some
> HW constraint like max current. In this case, the CPU might not reach
> max frequency even with an always running task.
> Then, beside frequency scaling, their is the uarch invariance that is
> introduced by patch 4 that will generate similar behavior of the load.

This is a 'common' issue. x86 and powerpc also suffer this. It can be
the result of either thermal or power thresholds.


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