RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v60]

[Markus Grönlund]

On Wed, 4 Jun 2025 19:38:57 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:
> 
>   Improve

src/hotspot/share/jfr/periodic/sampling/jfrCPUTimeThreadSampler.cpp line 634:

> 632: 
> 633: void JfrCPUSamplerThread::allow_signal_handlers() {
> 634:   Atomic::release_store(&_initialize_active_signal_handler_counter, (u4)0);

I think we might be getting a bit tired. I meant the function name, not the variable name, which now looks completely bonkers :-)

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2127323120