While performing load tests on a new system using RestEASY to provide atom feed representations, I discovered that the PermGen space was continually rising; I tracked this issue down to the AtomEntryProvider and AtomFeedProvider classes. From other things I've seen on the internet, it appears that the JAXB implementors intend for JAXBContext objects to be reused (e.g. see http://java.net/jira/browse/JAXB-581).
I'm attaching a patch with both a unit test and a fix for the two classes, switching them from using createContext to findCacheContext. Given the above issue, it may also be worthwhile to consider redesigning the JAXBContextFinder interface so that createContext is not exposed.