RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v5]

[Erik Gahlin]

On Fri, 23 May 2025 21:20:39 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> This is the code for the [JEP 509: CPU Time based profiling for JFR](https://openjdk.org/jeps/509).
>> 
>> Currently tested using [this test suite](https://github.com/parttimenerd/basic-profiler-tests). This runs profiles the [Renaissance](https://renaissance.dev/) benchmark with
>> - ... different heap sizes
>> - ... different GCs
>> - ... different samplers (the standard JFR and the new CPU Time Sampler and both)
>> - ... different JFR recording durations
>> - ... different chunk-sizes
>
> Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix compilation

test/jdk/jdk/jfr/event/runtime/TestActiveSettingEvent.java line 269:

> 267:         settingValues.put(EventNames.VirtualThreadSubmitFailed + "#threshold", "0 ns");
> 268:         settingValues.put(EventNames.SecurityProviderService + "#threshold", "0 ns");
> 269:         settingValues.put(EventNames.CPUTimeSampleLoss + "#threshold", "0 ns");

This should not be necessary for JVM events. JDK events are on the list because it was not possible to create instantaneous events in Java (it is now possible).

I see that the CPU Sample event has a duration. What does the duration field indicate when sampling?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2106301795