Tuesday, February 13, 2007

Escape Analysis in Mustang - I

EDIT: As commented by Brian, these Escape Analysis optimizations were dropped before final release and deferred to Java 7. The debug version of VM can no longer be found at http://download.java.net/download/jdk6/6u1/promoted/b03/binaries/jdk-6u1-ea-bin-b03-windows-i586-debug-19_jan_2007.jar. Production VM here means production release type, as compared to debug, not the final release.

Java 6 brings a lot of improvements in (much ignored) synchronization; like lock elision, adaptive locking etc., under, the awaited, escape analysis hood. I've been reading quite a bit on stack allocation and lock detection techniques to reduce GC overhead. (as stack comes for free; and sometimes, on full speed core).

Escape analysis is one of the interesting techniques in compiler optimization, read more here.

Few days back, I posted an off-topic curiosity on lang.java google group, It's not officially mentioned anywhere that escape analysis is implemented in mustang releases. Brian Goetz wrote an article stating EA is available in mustang builds, that article is pretty old and someone questioned whether it's really available or not...

A web search revealed that escape analysis *is* available in mustang (not well marketed?), and production VM binary (I've b-03) supports it out of the box in server mode; debug binaries supports few more switches to see the analysis. I'm trying to benchmark it with few programs playing around large number of object creation, not a big deal.

Well, if you are interested, try these switches with mustang (in server mode)
-XX:+DoEscapeAnalysis (works on production VM only).

May be this weekend, I'll post the results of the benchmarks and other findings on it.
Java's performance is getting better and better..

1 comment:

Brian said...

These features were dropped before release; the remaining work was deferred to Java 7.