During the hackathon I had some discussions around GC on large heaps.
This guy, who seems to know what he is talking about, and had a patch
accepted in hotspot jdk, said in 2011 that he's got a configuration working
reasonably well with large heaps at that time :
"I was able to keep GC pause on 32Gb Oracle Coherence storage node below
150ms on 8 core server."
There is a lot of stuff in his blog, some of it in Russian only, but at
least one of us will understand it.