Re: Hyper Threading on P4

[John McBride <jmcbride@xxxxxxxx>]

Matthias Bauw wrote:

> hi,
>
> I was in fact wondering how to get the most out of my P4 3.0Ghz with
> Hyper Threading.
>  
Watch out that the intel marketing monster doesn't kick you in the 
shorts. You still have only one CPU. Turning virtual CPUs on in our dual 
P4 boxes ("four"  CPUs) severely degraded the box performance. In many 
cases all turning on virtual CPUs does is make linux, under certain 
loads, to think "hey, I can shuffle things off to another CPU"--false in 
this case (it's the same CPU)  and there is overhead to swapping 
processes between CPUs, thus yielding "less than 0" performance increase.

---
John