Also see:
http://mark.koli.ch/understanding-javas-perm-gen-maxpermsize-heap-space-etc
http://stackoverflow.com/questions/10392255/permgen-space-error-in-tomcat
http://stackoverflow.com/questions/19404207/old-gen-heap-is-full-and-the-eden-and-survivor-are-low-and-almost-empty