RFR: 8322732: ForkJoinPool may underutilize cores in async mode [v3]

[Viktor Klang]

On Wed, 22 May 2024 15:32:42 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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 36 additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8322732
>  - More performance tradoffs
>  - Address review comments
>  - Merge branch 'openjdk:master' into JDK-8322732
>  - Repack some fields; adjust control flow
>  - Merge branch 'openjdk:master' into JDK-8322732
>  - Next version
>  - Merge branch 'openjdk:master' into JDK-8322732
>  - Reduce unneeded signals
>  - Merge branch 'openjdk:master' into JDK-8322732
>  - ... and 26 more: https://git.openjdk.org/jdk/compare/72365ee9...f1fc4f3e

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 586:

> 584:      * term. We use Marsaglia XorShifts, seeded with the Weyl sequence
> 585:      * from ThreadLocalRandom probes, which are cheap and
> 586:      * suffice. Each queue's polling attempt o avoid becoming stuck

Suggestion:

     * suffice. Each queue's polling attempt to avoid becoming stuck

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 597:

> 595:      * async mode.
> 596:      *
> 597:      * Deactivation. When no tasks are found by a worker in runWorker,

Suggestion:

     * Deactivation: When no tasks are found by a worker in runWorker,

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PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1610235852
PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1610239940