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Subject: Re: [OMPI users] How do I run OpenMPI safely on a Nehalem standalone machine?
From: Prentice Bisbal (prentice_at_[hidden])
Date: 2010-05-05 11:55:23

Gus Correa wrote:
> Hi Ralph
> Ralph Castain wrote:
>> One possibility is that the sm btl might not like that you have
>> hyperthreading enabled.
> I remember that hyperthreading was discussed months ago,
> in the previous incarnation of this problem/thread/discussion on
> "Nehalem vs. Open MPI".
> (It sounds like one of those supreme court cases ... )
> I don't really administer that machine,
> or any machine with hyperthreading,
> so I am not much familiar to the HT nitty-gritty.
> How do I turn off hyperthreading?
> Is it a BIOS or a Linux thing?
> I may try that.

HyperThreading can easily be turned off in the BIOS. At the risk of
starting a long off-topic discussion, I'm not sure HT is really needed
on non-Windows systems. I heard Intel added it to their processors to
get around deficiencies of the scheduler in Windows.

I'm not a hardware/operating system expert, so I'd google for more
definitive information. Or wait for someone else from this list to reply.