RFR: 8349763: Expose more ForkJoinPool parameters to configure virtual thread scheduler

[Jiawei Tang]

On Tue, 11 Feb 2025 02:36:14 GMT, Jiawei Tang <jwtang at openjdk.org> wrote:

> Since the parameters `-Djdk.virtualThreadScheduler.parallelism=N` , `-Djdk.virtualThreadScheduler.maxPoolSize=M`, `-Djdk.virtualThreadScheduler.minimumRunnable=Y` have already been made available, it would be worth considering opening up additional ForkJoinPool-related parameters: `-Djdk.virtualThreadScheduler.corePoolSize=X`, `-Djdk.virtualThreadScheduler.keepAliveTime=Z` and `-Djdk.virtualThreadScheduler.timeUnit`.
> 
> In particular, configuring corePoolSize can help reduce jitter caused by thread ramp-up during application startup, while keepAliveTime and timeUnit ensures more threads are available within the time expected by users. Opening these parameters would be highly meaningful for optimizing virtual thread scheduling.

Thank you. I get it. I will provide some data for discussion.

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PR Comment: https://git.openjdk.org/jdk/pull/23549#issuecomment-2650034999