Solving a PermGen issue on redeploy with Jetty 7

After a couple of days of debugging I have managed to have a medium-to-large web application redeploy successfully on Tomcat 6.0.32 without any PermGen leaks. I saw the PermGen drop after it filled, and the classloaders were garbage collected.

After much rejoicing I tried to make the application redeploy without leaks on our development environment, which is composed of Maven and the Jetty plugin.

Unfortunately I seem to have hit a server limitation, as illustrated by the below screenshot

Yourkit snapshot http://img811.imageshack.us/img811/7320/jettyclassloaderbeanelr.png

Jetty request threads have a strong reference to a BeanElResolver which in turns has a strong reference to multiple classes from my webapp.

I have found no reference on how to flush this information.

How can I remove this final PermGen leak from my application?

Update:

I've done the following to fix the problem, with no luck:

updated to the Latest version of the Jetty Plugin ( both 7.4.5 and 8.0.0.M3 )
used the CMS collector : -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled

Update 2:

I've reported this as a bug on the Jetty issue tracker: maven-jetty-plugin: PermGen leak due to javax.el.BeanELResolver

Solution

This is a actual bug in the EL implementation which is worked around in the latest Jetty versions.

Version 7.5.0, once released, will contain the fix.