linux-kernel - Re: [PATCH RFC 1/2] sched: cfs: introduce capacity

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Message-ID: <20141009190035.GB10832@worktop.programming.kicks-ass.net>
Date:	Thu, 9 Oct 2014 21:00:35 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mike Turquette <mturquette@...aro.org>
Cc:	Morten Rasmussen <morten.rasmussen@....com>, mingo@...hat.com,
	dietmar.eggemann@....com, pjt@...gle.com, bsegall@...gle.com,
	vincent.guittot@...aro.org, nicolas.pitre@...aro.org,
	rjw@...ysocki.net, linux-kernel@...r.kernel.org,
	tuukka.tikkanen@...aro.org
Subject: Re: [PATCH RFC 1/2] sched: cfs: introduce capacity_ops

On Thu, Oct 09, 2014 at 10:34:33AM -0700, Mike Turquette wrote:
> Quoting Peter Zijlstra (2014-10-09 02:00:24)
> > On Wed, Oct 08, 2014 at 04:28:36PM -0700, Mike Turquette wrote:
> > > > Yeah, like hell no. We do not want modules to affect scheduler
> > > > behaviour.
> > > 
> > > If a CPUfreq driver is the best place to know how frequency affects the
> > > capacity of a CPU for a given system, are you suggesting that we must
> > > compile that code into the kernel image instead of it being a loadable
> > > module?
> > 
> > Ideally we'll end up doing away with the cpufreq policy modules and
> > integrate the entire thing into the scheduler.
> 
> I said "CPUfreq driver", not "CPUfreq governor". Certainly the scheduler
> can pick a capacity state/p-state/frequency and, in doing so, replace
> the CPUfreq policy bits.
> 
> My question above was about the necessity to select the right CPUfreq
> driver at compile-time and lose support for those drivers to be loadable
> modules. Sounds like a bad idea.

Drivers should not care one way or another.
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