JBoss 5 Memory usage

Between JBoss 4 and JBoss 5 we have a big performance loss.
Looks like we are not the only one.

• http://community.jboss.org/message/557232
• http://seamframework.org/Community/BadPerformanceAfterMigratingToJBoss5x

First visible issue is memory consumtion :

• Nuxeo DM on Jboss 4.2 => 200 MB heap on startup
• Nuxeo DM on Jboss 5.1 => 700 MB heap on startup

This seems related to a VFS/JVM bug
https://jira.jboss.org/browse/JBAS-6549
https://jira.jboss.org/browse/JBVFS-159
https://jira.jboss.org/browse/JBAS-8066
http://bugs.sun.com/view_bug.do?bug_id=6735255