[TriLUG] Hyperthreading and Xeons
william at trilug.org
Thu Oct 14 02:11:05 EDT 2004
Would this be the reason that under Gentoo my dual Xeon 2GHz has a
tendency to lock up? I was using 2.4 stock kernels with HT enabled in the
On Wed, 13 Oct 2004, John Franklin wrote:
> On Oct 13, 2004, at 1:06 PM, Jeremy Portzer wrote:
> > So, I got my first Xeon server recently, and although it's really dual
> > 2.6 GHz, it shows as four processors to Linux.
> > Does this mean that I should treat it as a four-processor computer for
> > the purposes of starting processes? For example, I have a program that
> > runs as many copies of itself as there are processors (but you have to
> > tell it how many processors there are). Should I let it run four
> > copies
> > or stick with two?
> > Any other consequences to hyperthreading I should know about?
> 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.
> I don't know which Linux kernels (if any) are fully HT aware.
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