title: Eclipse extremely slow, continuously blocked in NonEssentialElementsFilter.hasFilteredChildren
body: <p>I have a long-lasting problem with eclipse, quite blocking, that started after eclipse Luna (no problem with Luna). For example, this problem is occurring with the most recent version of eclipse, whatever performance options I change (advised by other answers from stackoverflow).  </p>
  
  <p>With my quite big project (thousands of classes), eclipse is very slow (stuck several minutes or tens of minutes) quite randomly, when I open it, but later when I open project tree nodes, when I refresh, update the SVN working copy, etc.    </p>
  
  <p>Using JVisualVM, I can see that all the time is spent in <code>org.eclipse.jdt.internal.ui.navigator.NonEssentialElementsFilter.hasFilteredChildren</code> and, in fact, in <code>org.eclipse.jdt.internal.core.PackageFragment.getElementName</code> and </p>
  
  <pre><code>org.eclipse.jdt.internal.core.util.Util.concatWith...
  </code></pre>
  
  <p>I tried a lot of things (decorations, antivirus, breakpoints, recreating a new project, ...) but nothing helps.  </p>
  
  <p>And with Luna or previous versions, I did not have any problem like this. And I tried with a lot of newer versions, Mars, Neon JAVA only, Neon JEE, etc., they all have the same problem.  </p>
  
  <p>I hope someone can help, because it is quite blocking!</p>