2.4 Kernel and Hyperthreading (was Re: [Asterisk-Users] P4 processor with Hyperthreading and Asterisk)

[Jeremy McNamara]

mattf wrote:

>Is Asterisk's high memory usage canceling out most of the performance gained
>by using HT? 
>
>  
>

In my experience, I've found that hyperthreading is a major problem on 
Linux Kernel 2.4.   If I turn on hyperthreading and start to load up an 
Asterisk box we get ratty sounding audio along with pops, clicks and 
ticks, but if I disable hyperthreading (noht on the kernel line in 
lilo/grub) and all of those anomalies go away and the box scales a whole 
lot higher.

The problem is that the 2.4 Kernel sees the one hyperthreaded processor 
as two totally separate processors, so the 2.4 kernel tends to mess up, 
badly, when scheduling the processing.

This problem was delt with in the 2.5 kernel and i've been told by quite 
a few trusted people that it works flawlessly, but i'm not about to run 
a unstable kernel (or even anything less than like 2.6.14) on any of my 
production boxes.


Jeremy McNamara