linux-kernel - Re: bogomips discrepancy on Intel Core2 Quad CPU

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Message-ID: <Pine.LNX.4.64.0709031143540.27061@p34.internal.lan>
Date:	Mon, 3 Sep 2007 11:44:08 -0400 (EDT)
From:	Justin Piszcz <jpiszcz@...idpixels.com>
To:	Bill Davidsen <davidsen@....com>
cc:	bjdouma@...all.nl, linux-kernel@...r.kernel.org
Subject: Re: bogomips discrepancy on Intel Core2 Quad CPU



On Mon, 3 Sep 2007, Bill Davidsen wrote:

> Bauke Jan Douma wrote:
>> $> uname -a
>> Linux skyscraper 2.6.22.5 #7 SMP PREEMPT Sun Sep 2 12:12:25 CEST 2007 i686 
>> GNU/Linux
>> 
>> $> cat /proc/cpuinfo | grep bogomips
>> bogomips    : 4813.46
>> bogomips    : 4810.91
>> bogomips    : 4810.91
>> bogomips    : 10583.94
>> 
>> The latter seems way off base.
>> Prod me for more info.
>> 
> I see this occasionally on a dual, speedstep (or similar) finds a way to 
> throttle down the cores under light load. I suspect that if you load the 
> system:
>
>  for n in 1 2 3 4; do
>    nice -19 bash -c 'while true; do a=$RANDOM; done' &
>  done
>
> Then you should see your bogomips rise on all cores.
>
>
>> bjd
>
> 	[... copy of output snipped, see the O.P. ...]
>
> -- 
> Bill Davidsen <davidsen@....com>
>  "We have more to fear from the bungling of the incompetent than from
> the machinations of the wicked."  - from Slashdot
> -
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>

$ uname -a
Linux p34.internal.lan 2.6.22 #2 SMP Mon Jul 16 18:40:31 EDT 2007 x86_64 
GNU/Linux

$ cat /proc/cpuinfo | grep bogomips
bogomips        : 4797.72
bogomips        : 4795.16
bogomips        : 4795.21
bogomips        : 4795.19

Mine is fine, not using any speedstep here.

Justin.
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