Operating system tools are useless for determining JVM memory usage. The numbers that you printed include (most of the) heap, permgen, the binary code needed to run the JVM, the stacks and other misc non-Java stuff. If you want to know what is really going on use a tool such a jconsole of virtualvm. Those tools connect to a running JVM and can report heap and permgen usage. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4207027#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...