RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling

[Johannes Bechberger]

On Thu, 5 Jun 2025 06:29:15 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
>
> src/jdk.jfr/share/classes/jdk/jfr/internal/PlatformEventType.java line 203:
> 
>> 201:             this.cpuRate = rate;
>> 202:             if (isEnabled()) {
>> 203:                 JVM.setCPUThrottle(rate.rate(), rate.autoAdapt());
> 
> but we need to set the throttle somewhere? Else changes are not propagated?

I checked and it seems to work as expected

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PR Review Comment: https://git.openjdk.org/jdk/pull/25654#discussion_r2128055000