JBoss 7, java.lang.OutOfMemoryError: PermGen space

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I've hit this error where the CPU usage goes to its limits and JBoss needs a restart (java.lang.OutOfMemoryError: PermGen space).

I found a solution for older JBoss version to increase the MaxPermSize. I guess the same goes for JBoss7.

Which value would be good enough in order not to face any problem again? Is there any way to get permanently away from this problem (like lets say use a different VM like JRockit)?

jboss7.x webserver jakarta-ee jboss
4 Answers

Why it happens?

The "PermGen" error happens, when the Java virtual machine runs out of memory in the permanent generation. Recall that Java has a generational garbage collector, with four generations: eden, young, old and permanent. In the eden generation, objects are very short lived and garbage collection is swift and often. The young generation consists of objects that survived the eden generation (or was pushed down to young because the eden generation was full at the time of allocation), garbage collection in the young generation is less frequent but still happens at quite regular intervals (provided that your application actually does something and allocates objects every now and then). The old generation, well, you figured it. It contains objects that survived the young generation, or have been pushed down, and garbage collection is even less infrequent but can still happen. And finally, the permanent generation. This is for objects that the virtual machine has decided to endorse with eternal life - which is precicely the core of the problem. Objects in the permanent generation are never garbage collected; that is, under normal circumstances when the jvm is started with normal command line parameters. So what happens when you redeploy your web application is, that your WAR file is unpacked and its class files loaded into the jvm. And here's the thing: almost always ends up in the permanent generation... (taken from: http://rlogiacco.blogspot.com/2009/02/jboss-and-permgen-outofmemoryerror.html)

Here are some advices :

use this parameters for your JVM. they tell the Garbage Collector to invoke its algorithm also on the PermGen.

set JAVA_OPTS=-Xms512m -Xmx1024m 
-XX:PermSize=512m 
-XX:MaxPermSize=1024m 
-XX:+UseConcMarkSweepGC 
-XX:+CMSPermGenSweepingEnabled 
-XX:+CMSClassUnloadingEnabled
  • The CMSPermGenSweepingEnabled setting includes the PermGen in a garbage collection run. By default, the PermGen space is never included in garbage collection (and thus grows without bounds).
  • The CMSClassUnloadingEnabled setting tells the PermGen garbage collection sweep to take action on class objects. By default, class objects get an exemption, even when the PermGen space is being visited during a garabage collection.

Restart your JBOSS because each time you deploy application, you increase the amount of data in the PermGen.

You can also use JRocket JVM instead of the Sun JVM. it doesn't have any PermGen in its Garbage Collector algorithm.

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