linux-kernel - Re: [RFC PATCHC 3/3] sched/fair: use the idle state info to choose the idlest cpu

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Message-ID: <alpine.LFD.2.11.1404181159010.980@knanqh.ubzr>
Date:	Fri, 18 Apr 2014 12:00:44 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, rjw@...ysocki.net,
	linux-pm@...r.kernel.org, alex.shi@...aro.org,
	vincent.guittot@...aro.org, morten.rasmussen@....com
Subject: Re: [RFC PATCHC 3/3] sched/fair: use the idle state info to choose
 the idlest cpu

On Fri, 18 Apr 2014, Daniel Lezcano wrote:

> On 04/18/2014 02:53 PM, Peter Zijlstra wrote:
> > I suppose so; its still a bit like we won't but we will :-)
> >
> > So we _will_ actually expose coupled C states through the topology bits,
> > that's good.
> 
> Ah, ok. I think I understood where the confusion is coming from.
> 
> A couple of definitions for the same thing :)
> 
> 1. Coupled C-states : *mechanism* implemented in the cpuidle framework:
> drivers/cpuidle/coupled.c
> 
> 2. Coupled C-states : *constraint* to reach a cluster power down state, will
> be described through the topology and could be implemented by different
> mechanism (MCPM, handmade sync, cpuidle-coupled-c-state, firmware).
> 
> We want to expose 2. not 1. to the scheduler.

I couldn't explain it better.

Sorry for creating confusion.


Nicolas
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