Date: Sat, 8 Dec 2007 12:18:11 -0800
From: Arjan van de Ven <arjan@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Guillaume Chazarain <guichaz@yahoo.fr>,
       Thomas Gleixner <tglx@linutronix.de>,
       Stefano Brivio <stefano.brivio@polimi.it>, Robert Love <rml@tech9.net>,
       linux-kernel@vger.kernel.org, Dave Jones <davej@redhat.com>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, Michael Buesch <mb@bu3sch.de>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [patch] x86: scale cyc_2_nsec according to CPU frequency
Message-ID: <20071208121811.4e202804@laptopd505.fenrus.org>
In-Reply-To: <20071208191629.GB21186@elte.hu>
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	<20071208191629.GB21186@elte.hu>
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On Sat, 8 Dec 2007 20:16:29 +0100
Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Arjan van de Ven <arjan@infradead.org> wrote:
> 
> > > > > Firstly, we dont need the 'offset' anymore because
> > > > > cpu_clock() maintains offsets itself.
> > > > 
> > > > Yes, but a lower quality one. __update_rq_clock tries to 
> > > > compensate large jumping clocks with a jiffy resolution, while
> > > > my offset arranges for a very smooth frequency transition.
> > > 
> > > yes, but that would be easy to fix up via calling 
> > > sched_clock_idle_wakeup_event(0) when doing a frequency
> > > transition, without burdening the normal sched_clock() codepath
> > > with the offset. See the attached latest version.
> > 
> > can this deal with dual/quad core where the frequency of one core 
> > changes if the sofware changes the frequency of the other core?
> 
> doesnt the notifier still get run on the target CPU?
> 

.... if and only if the BIOS actually gives correct information to the
OS.

In reality... that's not a very common thing on this field sadly

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