I've unfortunately no ideas :-(, but encounter performance problems too.
We tested our web application by means of HttpUnit suite in 10 parallel processes. The same Java code (generated with xDoclet):
- WebLogic - stable, quick enough
- JBoss - instable, ending with no response
But we get a lot of "reentrant call detected..." exceptions. We will try to eliminate them and then repeat our tests.
JBoss 3.0.4-Tomcat 4.1.12, W2K - one processor ;-)