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

[Johannes Bechberger]

On Sun, 25 May 2025 20:40:02 GMT, Erik Gahlin <egahlin at openjdk.org> wrote:

>> 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?

How long the stack walking took. But it's probably irrelevant with the new design.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2106303459