Date: Fri, 7 Dec 2007 15:27:41 +0100
From: Guillaume Chazarain <guichaz@yahoo.fr>
To: Ingo Molnar <mingo@elte.hu>
Cc: 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: <20071207152741.3408aeef@inria.fr>
In-Reply-To: <20071207135525.GA5588@elte.hu>
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Le Fri, 7 Dec 2007 14:55:25 +0100,
Ingo Molnar <mingo@elte.hu> a écrit :

> 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.

I agree with keeping a single offset, but I liked the fact that with my
patch on frequency change, the clock had no jump at all.

> + *  ns += offset to avoid sched_clock jumps with cpufreq

I guess this needs to go away if I don't make my point :-(

> +	printk("CPU#%d: changed cyc2ns scale from %ld to %ld\n",
> +		cpu, prev_scale, *scale);

Pointing it out just to be sure it does not end in the final version ;-)

Thanks for cleaning up my mess ;-)

-- 
Guillaume
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