Could you please add

"Compressed oops is supported and enabled by default in Java SE 6u23 and later."

to the release notes of 6u23 ?

http://www.oracle.com/technetwork/java/javase/6u23releasenotes-191058.html

We have documented that at the Java 7 performance documentation ...

http://docs.oracle.com/javase/7/docs/technotes/guides/vm/performance-enhancements-7.html

... but there is no mention of it directly in the 6u23 Release Notes !

Technical verification:

 johann@tydirium:/extra/java/jdk/64/jdk1.6.0_23/bin$ ./java -XX:+PrintFlagsFinal -version | grep -i UseCompressedOops
  bool UseCompressedOops := true {lp64_product}
 java version "1.6.0_23"
 Java(TM) SE Runtime Environment (build 1.6.0_23-b05)
 Java HotSpot(TM) 64-Bit Server VM (build 19.0-b09, mixed mode)

 johann@tydirium:/extra/java/jdk/64/jdk1.6.0_22$ ./bin/java -XX:+PrintFlagsFinal -version | grep -i UseCompressedOops
  bool UseCompressedOops = false {lp64_product}
 java version "1.6.0_22"
 Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
 Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode)

For those who are interested in the motivation of this change request: the performance of my customer's application (app from Avaya, entitled) went poor after they have updated to 6u23+. Disabling the JVM option called UseCompressedOop gave us the good expected performance back. A testcase is not available since customer's app is quite complex and it has a lot of 3rd party code in it. Nonetheless, we believe that an improved 6u23 release note could have saved us time in isolating the problem.