RFR: 8322732: ForkJoinPool may underutilize cores in async mode

[Doug Lea]

On Fri, 10 May 2024 08:04:27 GMT, Viktor Klang <vklang at openjdk.org> wrote:

>> This set of changes address causes of poor utilization with small numbers of cores due to overly aggressive contention avoidance. A number of further adjustments were needed to still avoid most contention effects in deployments with large numbers of cores
>
> src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 1412:
> 
>> 1410:                         if (stalled)
>> 1411:                             Thread.onSpinWait();
>> 1412:                         stalled = true;
> 
> @DougLea Performance-wise, does it make any difference to make the write to `stalled` in an `else-branch` to avoid writing it every time beyond the initial?

This doesn't matter performance-wise but I agree that it looks unnecessarily odd so will change.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1596652131