[concurrency-interest] Performance regression in newest (6/20/2013) jsr166 update

√iktor Ҡlang viktor.klang at gmail.com
Wed Jun 26 11:23:00 EDT 2013


Hi Ron,

On Wed, Jun 26, 2013 at 5:13 PM, Ron Pressler <ron.pressler at gmail.com>wrote:

> > ... async mode (which is not common) ...
>
> AFAIK, all actor/messaging libraries that on FJ (like Akka and Quasar) use
> FJPool in async mode.
>

Yes, Akka and scala.concurrent relies heavily on the async mode.


>
> > Most of this can be reinstated though, which on a quick check of a quick
> touch-up recovers performance on your test case. Stay tuned.
>
> Great. Thanks.
> Obviously, FJ is mostly intended for batch parallelization, but it's such
> a good scheduler that online, low latency software is relying on FJ for
> scheduling. It would be a shame to sacrifice the async mode for the sake of
> the default mode. If it has to be done, maybe we should have different
> class for the async case?
>

Would be nice with a stripped-down version of FJP which only contains the
worker-local queues and the work-stealing.
Anyone up for that?

Cheers,
√


>
>
> On Wed, Jun 26, 2013 at 3:03 AM, Doug Lea <dl at cs.oswego.edu> wrote:
>
>> On 06/22/13 20:42, Ron Pressler wrote:
>>
>>> A couple of months ago I described the behavior detailed in the email
>>> exchange
>>> below. The newest update causes a slowdown of about 25% of this
>>> benchmark:
>>> ...
>>>
>>
>>
>>       static ForkJoinPool fjPool = new ForkJoinPool(PARALLELISM,
>>> ForkJoinPool.**defaultForkJoinWorkerThreadFac**tory, null, true);
>>>
>>
>> Yes, some handling for pools run in async mode (which is not common)
>> got a little worse in the course of improving vastly more common cases.
>> Most of this can be reinstated though, which on a quick check of
>> a quick touch-up recovers performance on your test case. Stay tuned.
>>
>>
>> -Doug
>>
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>
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-- 
*Viktor Klang*
*Director of Engineering*
Typesafe <http://www.typesafe.com/>

Twitter: @viktorklang
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