Recurring "PermGen" in Tomcat 6

Question

I keep getting a "PermGen" error on my Tomcat 6 server.

I know what application is causing the problem, but I am not sure why it is doing so. The application is using MySQL 5 and running on JDK 6.

Are there any tools/suggestions to diagnosis or analyze the underlying issue(s) with the specific application?

Thanks

Answer 1

The PermGen is used to store class definitions and the interned string pool.

Your code could be filling it (if it calls intern needlessly), but more likely is that the default is undersized for your application.

To set the permgen size, use "-XX:MaxPermSize=SIZE"

The following links may be helpful: tuning GC (this is the 1.5 edition), GC FAQ (1.4.2 edition), Hotspot VM options (I believe this is 1.6)

Answer 2

I think you might have many JSPs in your application. There is a known issue in tomcat where restarting a deployed application with many JSPs causes PermGen issues because tomcat recompiles and reloads all these classes again. Increasing the size as mentioned in the previous post should help.

Answer 3

Try the following JVM switches:

-XX:+UseConcMarkSweepGC -XX:+CMSPermGenSweepingEnabled -XX:+CMSClassUnloadingEnabled

Upping the permgen space with -XX:MaxPermSize just delays the problem.

Please see this comment: http://stackoverflow.com/questions/88235/how-to-deal-with-java-lang-outofmemoryerror-permgen-space-error/88262#88262

That indirectly pointed me to these two posts:

Problem: http://blogs.sun.com/fkieviet/entry/classloader%5Fleaks%5Fthe%5Fdreaded%5Fjava Solution: http://blogs.sun.com/fkieviet/entry/how%5Fto%5Ffix%5Fthe%5Fdreaded