We've seen some contention in several different performance tests related to RunAsListener. See http://mail-archives.apache.org/mod_mbox/tomcat-dev/200702.mbox/<45DD8... According to Remy in the thread above, the current implementation of InstanceSupport should not be used for anything other than debugging purposes. Maybe InstanceSupport could be changed to use some concurrent type, rather than array? --Phillip View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4022728#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...