What is Java's -XX:+UseMembar parameter

Question

I see this parameter in all kinds of places (forums, etc.) and the common answer it help highly concurrent servers. Still, I cannot find an official documentation from sun expla

Answer 1

I don't agree with answer from butterchicken. This page http://www.md.pp.ru/~eu/jdk6options.html says that this flag causes memory barriers to be issued then thread changes it's state (from RUNNABLE to WAITING or to BLOCKED, for example).