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Date: Thu, 11 Oct 2012 16:14:11 +0200
From: Andrea Suisani <sickpig@opinioni.net>
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To: Craig James <cjames@emolecules.com>
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Subject: Re: Two identical systems, radically different performance
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On 10/09/2012 01:40 AM, Craig James wrote:
> Nobody has commented on the hyperthreading question yet ... does it really matter? The old (fast) server has hyperthreading disabled, and the new (slower) server has hyperthreads enabled.
>
> If hyperthreading is definitely NOT an issue, it will save me a trip to the co-lo facility.


sorry to come late to the party, but being in a similar condition
I've googled a bit and I've found a way to disable hyperthreading without
the need to reboot the system and entering the bios:

echo 0 >/sys/devices/system/node/node0/cpuX/online

where X belongs to 1..(#cores * 2) if hyperthreading is enabled
(cpu0 can't be switched off).

didn't try myself on live system, but I definitely will
as soon as I have a new machine to test.

Andrea