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

[Johannes Bechberger]

On Mon, 26 May 2025 15:31:53 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> ![Screenshot From 2025-05-26 17-12-24](https://github.com/user-attachments/assets/9898d788-df61-4391-920a-fbecfa6b360c)
>
>> Sorry, you represent the sampling period value as ticks, not nanos. Its a Tickspan after all.
> 
> I don't. I represent it as a Tickspan, as I substract two TimeInstants:
> 
> 
>   TimeInterval<Rep, TimeSource> operator-(const TimeInstant<Rep, TimeSource>& start) const {
>     return TimeInterval<Rep, TimeSource>(*this, start);
>   }

Regarding JMC: I had to enable the experimental events in the preferences. Now it shows:

![image](https://github.com/user-attachments/assets/d31efde1-6075-4be6-b61f-91e5786637de)

So all is fine.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2107580724