linux-kernel - Re: [RFC 2/2] Make x86 calibrate

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Message-ID: <AANLkTinoctZFKo4wBmrrdFggnjSj74QfqvEpz59sW15x@mail.gmail.com>
Date:	Wed, 30 Mar 2011 21:46:46 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Robin Holt <holt@....com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [RFC 2/2] Make x86 calibrate_delay run in parallel.

On Tue, Dec 14, 2010 at 5:58 PM,  <Robin@....com> wrote:
>
> On a 4096 cpu machine, we noticed that 318 seconds were taken for bringing
> up the cpus.  By specifying lpj=<value>, we reduced that to 75 seconds.
> Andi Kleen suggested we rework the calibrate_delay calls to run in
> parallel.  With that code in place, a test boot of the same machine took
> 61 seconds to bring the cups up.  I am not sure how we beat the lpj=
> case, but it did outperform.
>
> One thing to note is the total BogoMIPS value is also consistently higher.
> I am wondering if this is an effect with the cores being in performance
> mode.  I did notice that the parallel calibrate_delay calls did cause the
> fans on the machine to ramp up to full speed where the normal sequential
> calls did not cause them to budge at all.

please check attached patch, that could calibrate correctly.

Thanks

Yinghai

View attachment "Make-x86-calibrate_delay-run-in-parallel.patch" of type "text/x-patch" (7417 bytes)