title: What does JVM flag CMSClassUnloadingEnabled actually do?
body: <p>I cannot for the life of me find a definition of what the Java VM flag <code>CMSClassUnloadingEnabled</code> actually does, other than some very fuzzy high-level definitions such as "gets rid of your PermGen problems" (<a href="https://stackoverflow.com/questions/3333807/the-various-options-for-solving-permgen-problems/3334397#3334397">which it doesn't</a>, btw).</p>
  
  <p>I have looked on Sun's/Oracle's site, and even <a href="http://blogs.oracle.com/watt/resource/jvm-options-list.html" rel="noreferrer">the options list</a> doesn't actually say what it does.</p>
  
  <p>Based upon the name of the flag, I'm guessing that the CMS Garbage Collector doesn't by default unload classes, and this flag turns it on - but I can't be sure.</p>