RFR: 8322732: ForkJoinPool may underutilize cores in async mode [v17]

[Viktor Klang]

On Fri, 31 May 2024 13:18:33 GMT, Doug Lea <dl 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
>
> Doug Lea has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Reconcile changes

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 2024:

> 2022:                                 }
> 2023:                                 if (pb == (pb = b))       // base unchanged
> 2024:                                     Thread.onSpinWait();

@DougLea Doesn't this mean that we'll always onSpinWait at least once here (since pb is initialized to -1 and not written until this check)

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1622475121