You set the MaxPermSize but not the starting value: add "-XX:NewSize=128m" to the parameter list. Don't know much about the flags "-XX:+UseParNewGC" and "-XX:+CMSParallelRemarkEnabled" and JBoss on Linux, but I would try to run without it. JDK 1.5 checks the system for available CPUs and memory and set's values based on that. You also may add "-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:-TraceClassUnloading" to see GC messages and see if there are messages generated constantly when the CPU load increases. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4026999#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...