[concurrency-interest] ForkJoin for Java5

Doug Lea dl at cs.oswego.edu
Fri Apr 23 10:32:07 EDT 2010


On 04/23/10 09:26, Denys Geert wrote:
> Hi,
>
> As far as I remember, there is no Java5 backport of FJ, because the
> performance degradation would be significant. I was wondering if anybody
> could quantify this.
>
> We may be looking to backport FJ to Java5 to support a few customers that
> insist on Java5 for the time being. Having some reduced performance is
> acceptable, but it would be good to know what we can expect before taking on
> the backport.
>
> If anybody has experience with this or can venture an educated guess, that
> would be very helpful. Also, what are the major dependencies on Java 6?
>

It depends on the machine, but a quick check across ones
I have around here shows slowdown averaging around 30%,
generally worse for machines with more processors.

The main impact is the loss of lazySet (actually, its Unsafe mapping)
which you need to replace with plain volatile writes.

-Doug


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