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Editorial Team
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Asked: 2026-05-14T06:01:05+00:00

I’m playing around with writing some simple Spring-based web apps and deploying them to

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I’m playing around with writing some simple Spring-based web apps and deploying them to Tomcat. Almost immediately, I run into the need to customize the Tomcat’s JVM settings with -XX:MaxPermSize (and -Xmx and -Xms); without this, the server easily runs out of PermGen space.

Why is this such an issue for Java VMs compared to other garbage collected languages? Comparing counts of “tune X memory usage” for X in Java, Ruby, Perl and Python, shows that Java has easily an order of magnitude more hits in Google than the other languages combined.

I’d also be interested in references to technical papers/blog-posts/etc explaining design choices behind JVM GC implementations, across different JVMs or compared to other interpreted language VMs (e.g. comparing Sun or IBM JVM to Parrot). Are there technical reasons why JVM users still have to deal with non-auto-tuning heap/permgen sizes?

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1 Answer

  1. Editorial Team

    The title of your question is misleading (not on purpose, I know): PermSize issues (and there are a lot of them, I was one of the first one to diagnose a Tomcat/Sun PermGen issue years ago, when there wasn’t any knowledge on the issue yet) are not a Java specifity but a Sun VM specifity.

    If you use a VM that doesn’t use permanent generation (like, say, an IBM VM if I’m not mistaken) you cannot have permgen issues.

    So it’s is not a “Java” problem, but a Sun VM implementation problem.

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