title: OldGen usage goes up after Full GC
body: <p>Trying to debug a memory leak in a java program (running on linux 64bits), using VisualVM 1.3.</p>
  
  <p>I noticed that after each click on the "Perform GC" button  in the VisualVM Monitor tab, the "used" value for the Old Gen memory pool goes up... which seems rather counter-intuitive... </p>
  
  <p>That would make sense if "Perform GC" did trigger a GC for the young gen only (since some objects could then be migrated from young to old gen)... But not in the case of a full GC.</p>
  
  <p>Has anyone has encountered this before ?  Thanks.</p>
  
  <p>Eg.
  1) OldGen Initial state:</p>
  
  <p>PeakUsage
  committed:1431 Mb
  init:1431 Mb
  max:1431 Mb
  used:98Mb</p>
  
  <p>Usage
  committed:1431 Mb
  init:1431 Mb
  max:1431 Mb
  used:98Mb</p>
  
  <p>2) Perform GC</p>
  
  <p>3) New state:</p>
  
  <p>PeakUsage
  committed:1431 Mb
  init:1431 Mb
  max:1431 Mb
  used:105Mb</p>
  
  <p>Usage
  committed:1431 Mb
  init:1431 Mb
  max:1431 Mb
  used:105Mb</p>