Re: Disable of hyperthreading on Xeon

From: Christopher Browne (cbbrowne_at_acm.org)
Date: 12/02/03 

Date: 2 Dec 2003 02:41:37 GMT

Clinging to sanity, Brandon Niemczyk <maccorin@cfl.rr.com> mumbled into her beard:
> On Tue, 02 Dec 2003 08:54:15 +0800, David YEUNG wrote:
>
>> I've a Dual CPU Xeon machine running RedHat 9 (kernel 2.4.20 SMP mode).
>> When I boot up the machine, it shows 4 CPUs because of the hyperthreading.
>> Is there anyway in RedHat to disable the hyperthreading so that only two
>> physical CPUs can be seen?
>
> AFAIK you should be able to disable it in your bios, but why would you
> want to do this? I'm sure there is a performance loss

Why are you certain that there would be a performance gain?

The theoretical "best" results seem to involve getting about a 20%
boost, and it seems easy for "dueling cache misses" to lead to
performance losses. 

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