Why is PermGen space growing?

Question

I've read a few articles, and I understood the following (please correct me and/or edit the question if I'm wrong):

The java heap is segmented like this:

• Young Generation: objects that are created go here, this part is frequently and inexpensively garbage collected

• Old Generation: objects that survive the garbage collections of the Young generation go here, this area is garbage collected less frequently and using a more CPU demanding process/algorithm (I believe it's called mark-sweep)

Edit: as stated by another user, PermGen is not a part of the region called heap

• PermGen: this area is filled of your app classes metadata and many other things that do not depend on the application usage.

So, knowing this... why does my PermGen space grows when the app is under heavy load? For what I said before this space should not incrementally fill in spite of the app load, but as I said in the beginning probably I'm wrong about some assumptions.

In fact if the PermGen space is growing, is there a way of garbage collect or reset it?

Answer 1

This is one of the more annoying problems to debug. There are a lot of reasons you could be seeing growing permgen use. Here are 2 links I found very useful in both understanding how leaks happen as well as tracking down what is causing them.

http://frankkieviet.blogspot.com/2006/10/how-to-fix-dreaded-permgen-space.html

http://frankkieviet.blogspot.com/2006/10/classloader-leaks-dreaded-permgen-space.html