Shashi Velur’s blog

Today, during load testing I saw one of those dreaded “java.lang.OutOfMemoryError: PermGen space” errors on our fairly large web application deployed in Tomcat running on Sun JDK 1.5.

We used to use the default (64m) for the perm space. I bumped it to 128 for now, until I can find some time to dig into this using JProfiler and JHAT.

I will be particularly looking at the amount of our classes loaded from WEB-INF/classes dir (we have a lot of generated classes from legacy code), Static references in our legacy code, Spring AOP/Hibernate CGLib usage and ThreadLocal usage in our application.

I found some useful information here:

• http://opensource.atlassian.com/confluence/spring/pages/viewpage.action?pageId=2669
• http://my.opera.com/karmazilla/blog/2007/09/29/return-of-the-permgen
• http://blogs.sun.com/fkieviet/entry/how_to_fix_the_dreaded
• http://blogs.sun.com/sundararajan/entry/querying_java_heap_with_oql

Technorati Tags: OutOfMemoryError, Performance tuning

I am currently working on performance tuning & refactoring a product. And, interestingly I found some Agile/Lean principles that apply for performance tuning and refactoring:

• Most Lean principles appear counter-intuitive at first
• Aim for system optimization instead of point optimization
• Build prototype and measure (run quick experiments), not just theorize
• Minimize the number and size of things-in-process
• The most predictable performance comes from maintaining options until you have the most information

Technorati Tags: Agile, Lean principles, Performance tuning