Re: [condor-users] Pc's with hyperthreading

[Erik Paulson <epaulson@xxxxxxxxxxx>]

On Fri, Apr 23, 2004 at 10:30:32AM +1000, Ian.McLeod@xxxxxxxx wrote:
> Our latest crop of Pc's are coming with hyperthreading 
> The computers are pretending to have 2 cpu's
> 
> Two questions 
> 1. How do I want to convince condor that it really has only one CPU
>    I found the NUM_CPUS in the config file - 
>    but I note that its use is not recommended. 
> 

For disabling hyperthreading, that is the recommended solution.
Many machines will let you disable hyperthreading in the BIOS
as well.

In Condor 6.6.5 (still a few weeks off), we have a 
COUNT_HYPERTHREAD_CPUS = FALSE

option, which will detect if some of the CPUs are hyperthreads
and not count them, so you can set this as a global config file.

It's currently a Linux-only option, we'll see if we can make it work
on Windows too.

> 1. How good is the hyper-threading technology ? 
>    Should I be trying to convince condor that it really has only one CPU

As with all things HPC, it depends on the app :)

For the most part, here at UW we've disabled it to keep the RAM per 
virtual machine high.

-Erik
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