RFR: JDK-8319662 ForkJoinPool trims worker threads too slowly [v8]

[kerr]

On Mon, 4 Dec 2023 13:56:55 GMT, Doug Lea <dl at openjdk.org> wrote:

>> This update cascades timeouts to trim subsequent workers after the first  keepAlive inactive period.
>
> 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 10 additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8319662
>  - Remove unnecessary re-interrupt
>  - Merge branch 'openjdk:master' into JDK-8319662
>  - Reduce oversignalling and contention; add test
>  - Revert 2 lines in method scan
>  - Merge branch 'openjdk:master' into JDK-8319662
>  - Split up method awaitWork; other associated changes.
>  - Merge branch 'openjdk:master' into JDK-8319662
>  - tweak cascades; reinstate an @Contended; resolve JDK-8319498
>  - Support cascading idle timeouts

Cool, I just encounter this problem, when I migrate to Virtual threads and set  `jdk.virtualThreadScheduler.maxPoolSize` to 2500.

Will this change backport to j21u, thanks.

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PR Comment: https://git.openjdk.org/jdk/pull/16725#issuecomment-1889239126