RFR: 8322732: ForkJoinPool may underutilize cores in async mode

[Viktor Klang]

On Tue, 7 May 2024 22:50:18 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

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 599:

> 597:      * Deactivation. When method scan indicates (twice) that no tasks
> 598:      * are found by a worker, it tries to deactivate()), giving up
> 599:      * (and rescanning) on ctl contention. To avoid missed signals

Suggestion:

     * (and rescanning) on "ctl" contention. To avoid missed signals

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 880:

> 878:      * updated by owners from those most commonly read by stealers or
> 879:      * other management.  For class WorkQueue, an embedded padded
> 880:      * region segregates fields (all decalred as "int") most heavily

Suggestion:

     * region segregates fields (all declared as "int") most heavily

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PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1597520813
PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1597520717