RFR: 8360046: Scalability issue when submitting virtual threads with almost empty tasks [v16]

[Viktor Klang]

On Sun, 9 Nov 2025 16:38:06 GMT, Doug Lea <dl at openjdk.org> wrote:

>> This set of updates reduces contention-based performance loss under heavy over-subscription, while also improving perfomance more generally.
>
> 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 25 additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8360046
>  - Seperate repolling policies
>  - Faster quiescent termination
>  - Fix push, refactor deactivate
>  - Use absolute timed waits
>  - Reduce deactivate/reactivate and cancelled timeout rates
>  - Merge branch 'openjdk:master' into JDK-8360046
>  - Reduce park/unpark rates
>  - Add @Contended WorkQueue region. Adapt accordingly.
>  - Revert Exchanger for separate PR
>  - ... and 15 more: https://git.openjdk.org/jdk/compare/a2d555de...0f2f5908

src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 2059:

> 2057:                                 rescans = 1;
> 2058:                                 if (nt != null &&         // confirm a[nk]
> 2059:                                     U.getReferenceAcquire(a, np) == nt)

👍

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PR Review Comment: https://git.openjdk.org/jdk/pull/26479#discussion_r2509671315