We have hard from several customers that sometimes Full GCs with CMS can be "really fast". Here's an example"

152.070: [Full GC 152.070: [ParNew: 1226496K->0K(1227648K), 0.0415750 secs]
2452329K->1247682K(4914048K), 0.0418400 secs]

Actuallly, the above is not a full GC but a young GC forced after a (or many) JNI critical sections prevented the GC from happening earlier and forced it when it/them completed. However, it has been clearly mislabelled as a Full GC. This should be something easy to fix that will stop confusing customers (and us too!).