RFR: 8360046: Scalability issue when submitting virtual threads with almost empty tasks [v19]

[Doug Lea]

On Mon, 24 Nov 2025 16:13:34 GMT, Viktor Klang <vklang at openjdk.org> wrote:

>> 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 29 additional commits since the last revision:
>> 
>>  - Merge branch 'openjdk:master' into JDK-8360046
>>  - Signal on setParallelism
>>  - Drop added Contended region; simplify accordingly
>>  - Tweaks
>>  - 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
>>  - ... and 19 more: https://git.openjdk.org/jdk/compare/7edd4d73...383f9238
>
> src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 3339:
> 
>> 3337:             throw new UnsupportedOperationException("Cannot override System property");
>> 3338:         if ((prevSize = getAndSetParallelism(size)) < size)
>> 3339:             signalWork(null, 0);
> 
> Suggestion:
> 
>             signalWork(null, 0); // trigger worker activation

thanks; done.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26479#discussion_r2557168773