[concurrency-interest] ForkJoin updates

Jason Mehrens jason_mehrens at hotmail.com
Fri Feb 3 11:29:22 EST 2012

Hi Doug,
Would unconditionally marking the ForkJoinTask as ineligible for biased locking, as described in http://blogs.oracle.com/dave/entry/biased_locking_in_hotspot, offer the same performance improvement as system wide disabling of biased locking?
According to this, http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6378256, you might want to test transforming System.identityHashCode(this) into super.hashCode() when that transformation is safe to perform.

> 5. Other minor changes that give a few percent improvement in
> common FJ task processing. On the other hand, this version is
> even more prone to GC cardmark contention. So if using hotspot
> on a multiprocessor (or even >4core multicore) you absolutely
> must run in -XX:UseCondCardMark or -XX:+UseG1GC. (Also, it is
> better behaved with biased locking disabled -XX:-UseBiasedLocking).
> As always, suggestions and comments based on usage experience
> would be very welcome.
> -Doug
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