Hi, switching to an IBM JVM not only yields better performance on Linux, in my experience also on my development (win XP) box in comparison with the old Sun 1.3 JVM. When our app is going live we'll definately use Linux combined with IBM's JVM, the speed increase is the bomb.
Anyways, thanks for your hints
from where you download the ibm jdk 1.4 for windows ?
The results seem impressive. I haven't personally seen a huge jump in performance but a lot of the I/O improvements in Sun JDK 1.4.1 were a result of IBM's 1.3 tweaking. The bottleneck for my system is probably my DB server so it is hard to judge.
You can get the IBM SDK (as they call it) from the Developer World part of their website. Actually it is quicker to search Google and then let Google guide you to the right area. You will need a Developer World login to download the SDK - about 70Mb worth.
You will also have a few things to do. Tomcat SSL won't work with it standard because it doesn't allow for the IBM JSSE provider - I couldn't find a patch for it. So you will need to go with Jetty and compile in the contrib from a Jetty 4.2.9 distribution to work with JBoss 3.2.0. For this, you need to drop the security.jar from the IBM SDK into the Jetty source ext directory. You will also need to do some performance tweaking with the standard Jetty distribution. I got lazy and just dropped the compiled IbmJsseProvider class into the org.mortbay.jetty.jar that came with JBoss 3.2.0.
Some other things to note. The IBM SDK environment seems to take up about 30 Mb ~ 40 Mb more memory than the Sun JDK 1.4.1_01 running in Linux. It can take the RSS footprint for JBoss-Jetty to about 140 Mb to 150 Mb as opposed to about 110 Mb with a Sun JDK.
If you are running Tomcat, you'll find the footprint a little bigger as Jetty is comparatively small.
Hope that helps if you are considering the IBM SDK.