RFR: 8292969: Bad Thread Utilization in ForkJoinPool

[Doug Lea]

On Mon, 26 Sep 2022 13:21:23 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> 8292969: This small change in signal propagation rules improves utilization when entry queues are resized,
>
> src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 1842:
> 
>> 1840:                         signalWork();           // propagate at most twice/run
>> 1841:                     w.topLevelExec(t, q);
>> 1842:                     return src + (prevSrc << SWIDTH);
> 
> Are all of these values (`src`, `prevSrc`) less or equal `0x7FFF`? Otherwise we are playing with sign bits here.

Yes, see the discussions around line 391 of internal docs.

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PR: https://git.openjdk.org/jdk/pull/10198