Re: [gentoo-server] Gentoo on Pentium IV with Hyper-Threading

[Andy Dustman]

On Thu, 2004-03-18 at 09:35, Nick Van Vlaenderen wrote:

> I am going to install Gentoo Linux on a server with a Pentium IV CPU
> with Hyper-Threading. My question is, does anyone has experience with
> that kind of servers? I know that I need to enable SMP in the kernel,
> but do I need to use something specific to make Gentoo use the 2
> virtual CPU's and not only one? And how can I have better performance
> .. and so on?

Yes, enable SMP. If HT is really enabled for your box (in the BIOS), it
should just work. If you happen to use an 2.6 series kernel, you have
the option of specifying the maximum number of processors to support;
set this to twice the number of real processors, i.e. the total of real
and virtual processors.

In my experience with a dual 2.4 GHz P4-Xeon system, the optimal make
parallelism setting is -j4. I found that I could compile the 2.6 kernel
in about 3:40 clock time, although I was not (according to time) using
100% CPU (slightly less than 10 min CPU time). Usually my rule of thumb
is twice the number of processors, so I tried -j8 (did I mention 1 GB of
RAM?). This reduced the compile time very slightly (about 3:20), and
essentially maxed out the CPU time (over 12 min). But clock time is the
thing that really matters, and the improvement was so small I decided to
stick with -j4.

This is a *very* simple benchmark, and doesn't account for things like
caching and such, so don't draw too many conclusions.

-- 
Andy Dustman <adustman@×××××××××.edu>
Office of Information Technology, Terry College of Business, UGA