RFR: 8322732: ForkJoinPool may underutilize cores in async mode [v7]

[Viktor Klang]

On Wed, 29 May 2024 11:33:40 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 41 additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8322732
>  - Add test for utilization with interdependent tasks
>  - Un-misplace onSpinWait call
>  - Adjust control flow
>  - Reduce memory stalls
>  - 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
>  - ... and 31 more: https://git.openjdk.org/jdk/compare/9388a872...cf5fe55c

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 912:

> 910:      * enough to avoid resizing in most tree-structured tasks, but
> 911:      * larger for external queues where both false-sharing problems
> 912:      * and the need for resizing are more common..  (Maintenance note:

Suggestion:

     * and the need for resizing are more common.  (Maintenance note:

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PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1618884462