I noticed this occurrence in big application where the front end server was gobbling up PermGen quite fast, worst part it kept on increasing on every request, sometimes it just keeps on increasing even though we don't do any request to the application server at all. I faced this with tomcat 6.0.33, tomcat6.0.29 both.
To isolate the problem I picked up struts blank and to my dismay it was showing the same trend. Is this normal? I tried checking out a few version of struts2 like 2.2.1, 2.2.1.1, 2.2.3.1 using maven (mvn archetype:generate) and after running them in jetty, I noticed that the PermGen space is filled up in every request by 2-3KB. I am testing on struts blank and jetty-6.1.21.
Since PermGen is increasing as a function of number of request I suspect how much worthy is it to go to production with it?
The only way to know for sure is to attach a profiler and look at which classes are taking up the most memory, and try to find a memory leak. You can configure you jvm to dump the heap on crash, and load the resulting file into a profiler to look at the state of the heap when it crashed.
Struts is used in many production web apps. I think it is more likely a problem with your app.