I set up a simple webapp (with :dependencies [[org.clojure/clojure "1.6.0-RC1"]]) and a handler that just returned an empty string, so nothing fancy.
Start immutant with "lein immutant run" and use VisualVM to inspect permgen. Consistently increases 12Mb every deploy.
Also tried running with -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled but it did not fix the issue.
Update: Seems to be an issue with Oracle JDBC, since simply adding a JDBC library will cause leak in Permgen. http://jrfom.com/2014/01/08/fu-ojdbc/