[ILUG] My venture into 2.6 kernel on an older desktop...

[Glen Gray]

As my friends on the list will know, I've a somewhat out dated by todays
standards desktop PC. To be honest it's not that bad a machine (as long
as PC games aren't your thing) but as technology marches ever forward
i.e. software bloat and you know you just have to have all those lovely
wiz bang features, things really start to get bogged down. Being an avid
Gnome fan I wanted to keep up with the desktops as they progressed.

However I found RedHat 8 and 9 to be far too cumbersome on my Pentium II
450. I'd plenty of ram, but switching from desktop to desktop seemed far
to painful. I was slowly reverting back to a Windows way of doing things
(i.e. 1 desktop, things I wasn't using minimized etc). I wasn't too
happy about this. In an effort to squeeze a little more life out of my
once top of the range PC I decided to give Gentoo a run. Now I know lots
of you out there are skeptics over the whole Gentoo way of doing things.
All I can say is that I was impressed with the results. So much so that
it's been on my desktop ever since. It's painful to setup at first on
older machines, but once up and running you'll feel the benefits. 

So at the end of last week I decided to give the 2.6.3 kernel a run
using the gentoo-dev-sources. These are patched sources with mostly
AMD64 stability fixes that I can see from the website. The previous
kernel was a gentoo modified 2.4.22. This was based off the ck patch
set. 

My first reaction was "WOW". The desktop really was more responsive. The
speed increase was on a par with what I felt when trying Gentoo on this
machine for the first time last year. It's very hard to quantify why
something seems faster to someone that hasn't gone through the same
thing. Screen redraws happening much quicker is what really caught my
attention and little or now UI performance decrease when you've a
compile going on in the background.

Next I set about testing if it performed any better other than visually.
I was slightly disappointed with my initial results. I've not had time
to get back to them, but perhaps I will this week. Some tips on what to
and what not to include in the kernel are welcome.

On Gentoo there is a convenient little script called genkernel that you
can use to generate a kernel image and and initrd image and have it
installed in /boot. The script stores your config in a
/usr/share/genkernel/kernel-2.x.config file and reuses it. It does a
make mrproper, followed by a make oldconfig before doing the actual
kernel compile. Then it copies the kernel to /boot, builds an initrd
image and copies that to /boot too. 

First of all I generated a config I was happy with (only some minor
changes, still a lot of modules that I'll never need) and then set about
timing how long it would take to do the full compile on the 2.4.22
gentoo kernel and then the 2.6.3 gentoo kernel. I found that it took the
2.6.3 kernel about 20+seconds longer to complete the task on average.
This was from a console with no X/xfs running. I don't have any server
programs running on that PC either. 

Hopefully I'll get time this week to try out a vanilla 2.6 kernel and
see how that compares.

One other thing I tested was converting a DVD to an SVCD. There was no
change in the the fps that transcode was able to process. Obviously a
CPU bound computational task. 
-- 
Glen Gray <glen at lincor.com>                             17 Dame Court
Senior Software Engineer                            Dublin 2, Ireland
Lincor Solutions Ltd.                          Ph: +353 (0) 1 6746413