[Beowulf] performance tweaks and optimum memory configs for a Nehalem

Renato Callado Borges renato.oferenda at gmail.com
Mon Aug 10 08:43:49 PDT 2009

On Mon, Aug 10, 2009 at 08:33:27AM -0400, Mark Hahn wrote:
>> Is there a way of finding out within Linux if Hyperthreading is on or
>> not?
> in /proc/cpuinfo, I believe it's a simple as siblings > cpu cores.
> that is, I'm guessing one of your nehalem's shows as having 8 siblings
> and 4 cpu cores.

Googling for 'dmidecode Hyper Thread' I found this 2004 article:


And it says:

"I would have liked to just read /proc/cpuinfo to determine if Hyper-Threading is enabled, but currently that info is not exported to that file. /proc/cpuinfo just displays the number of physical CPUs in the system and ignores Hyper-Threading.

The process of using x86info is similar to the process of using dmidecode: execute and parse the output. In this case, x86info will say _The physical package supports 2 logical processors_ if Hyper-Threading is enabled on a standard Xeon system."

Installed x86info in my box, ran it and (correctly) it says my box' physical package supports 1 logical processor. (It's a Pentium 4).

[]'s, RCB.

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