CODEWITHSUNDEEP
javajboss
Navnath
Navnath

Reputation: 53

PermGen space exception

I m using JAVA 5 (32 bit) for my application running on JBoss. But it working fine only for 32bit. As we deploy it on 64bit java5, it throws an Exception

"java.lang.OutOfMemoryError: PermGen space" exception

Is there any Patch required? Is any code code change required?

Thanks in advance.

Upvotes: 4

Views: 10286

Answers (4)

gigadot
gigadot

Reputation: 8969

I have got the same prolem when I run my web application under tomcat or jetty. Permanent genration memory is used for loading the classes and the idea is that "Classes are loaded once and forever". Since I am using quite a lot of libraries and Spring framework, this memory is filled up very quickly espectially when I redeploy the web application several time with out restarting the servlet container.

I found that increasing the maximum permanent generation is not sufficient. You also need to allow the garbage collection to removed the unused classes at runtime, otherwise it will be filled up and throws PermGen space exception. Here are the JVM options that I added for my servlet containers,

-XX:PermSize=128m -XX:MaxPermSize=256m -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled

-XX:MaxPermSize is used to set the maximum value of permanent generation. This should be greater than the default size.

-XX:+CMSClassUnloadingEnabled this option is used to allows JVM to unload the class at runtime. By default, class unloading is disable. For Java 5, please read this.

-XX:+UseConcMarkSweepGC, in order for class uploading option to work, this option must also be set (ref)

Also, you should consider upgrading your JVM version. Java 5 is too old.

Upvotes: 7

Nirmal
Nirmal

Reputation: 4829

Create one environment variable with following parameter/values :

varible name = JAVA_OPTS

variable value = -Xmx1000M -XX:MaxPermSize=512m

Upvotes: 0

Peter Lawrey
Peter Lawrey

Reputation: 533530

Is there any Patch required?

Yes, Using the 64-bit Java 6 or 7 which uses 32-bit references by default. Java 5.0 uses 64-bit references. I don't imagine this will be added to Java 5.0 as it hasn't been freely supported for almost two years. (You can pay to support it BTW)

In the Sun/Oracle JVM, objects are 8 byte aligned. The JVM uses this fact to use 32-bit references to address 32 GB of memory. (8 * 4G). With direct and memory mapped memory you can use more than 32 GB.

Upvotes: 2

9000
9000

Reputation: 40894

64-bit Java has twice as long pointers as 32-bit has. Since most of your objects are composed of pointers (references to other objects), you need significantly more memory to run. You run a 64-bit version because your app needs more than 4GB allocated in the first place, don't you? If you don't, you're better off with a 32-bit JVM.

Play with -XX:MaxPermSize= when starting your server.

Upvotes: 3

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