Open launch configuration and add the following to the VM arguments.
-Xms768m -Xmx1024m -XX:MaxPermSize=512m
OutOfMemory in PermGen on Tomcat may not be just because of in sufficient memory but also due to serious leak as explained in <a href="http://javarevisited.blogspot.sg/2012/01/tomcat-javalangoutofmemoryerror-permgen.html>PermGen memory leak in Tomcat</a>. As Tomcat use different classloader to load different web app.
PermGen memory leak in Tomcat