[TriLUG] Hyperthreading and Xeons

[Jeremy Portzer]

On Wed, 2004-10-13 at 17:47, John Franklin wrote:

> One of the big issues with HT is that it looks like SMP to HT-unaware 
> kernels.  The difference between SMP and HT is the shared resources on 
> the chip.  When moving a process to a second CPU (core), an HT-unaware 
> kernel may blow the CPU cache, move the process to the second core 
> thinking it's a physically separate CPU, and refill the CPU cache.  An 
> HT-aware kernel will move the process w/o blowing the cache.
> 

Would it therefore be prudent to turn off HT if your application is
memory-intensive?  Is it even possible to turn off HT (e.g. BIOS
setting)?  If I can turn it off, I guess I could try to do some
benchmarks with my particular application...

I'm using kernel 2.4.21 with Red Hat's modifications, on CentOS 3.3.

Jeremy

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