Scott Carey wrote:
The implementation in JRE 6u14 uses a shift for all heap sizes, the
optimization to remove that for heaps less than 4GB is not in the hotspot
version there (but will be later).
OK. I've been using JRockit 64 bit for a while, and it did a check on
every pointer to see if it was real or relative, then an add, so I
suspect its computation was more complex. The sun approach seems better
The size advantage is there either way.
I have not tested an app myself that was not faster using
-XX:+UseCompressedOops on a 64 bit JVM.
The extra bit shifting is overshadowed by how much faster and less frequent
GC is with a smaller dataset.
Excellent.
You get better cache efficiency too -less cache misses, and save on
memory bandwidth
