Virtual Threads without Pinning

I am trying to show the performance benefits of the new feature in JDK 24

JEP 491: Synchronize Virtual Threads without Pinning

I understand there is some logic to benchmarking, but I can't seem to figure this one out. I have tried everything from increasing the number of threads to limiting the number of platform threads -Djdk.virtualThreadScheduler.parallelism=1 and no matter what I do I can show the performance benefits of JDK 24 vs 21.

The limited number of carrier threads (1) should pin the virtual thread to the carrier thread and make it unavailable to do any other work making this application run much slower on JDK 21.

// This work can run concurrently if carrier threads are available.
doCpuWork();
synchronized (lock) {
    // Short sleep *inside* the lock
    // JDK 21: Pins carrier, making it unavailable for others' doCpuWork()
    // JDK 24: Unmounts carrier, allowing it to run others' doCpuWork()
    Thread.sleep(Duration.ofMillis(BLOCKING_TIME_MS));
}

These are the results I am getting

Running with Java version: 21.0.6
Launching 5,000 virtual threads...
Each thread does CPU work (10,000 iterations), then acquires lock and blocks for 5 ms.
All 5,000 tasks completed.
Total execution time: 32.334 seconds
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Running with Java version: 24
Launching 5,000 virtual threads...
Each thread does CPU work (10,000 iterations), then acquires lock and blocks for 5 ms.
All 5,000 tasks completed.
Total execution time: 31.592 seconds
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