RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v26]

[Markus Grönlund]

On Sun, 1 Jun 2025 07:26:19 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 two additional commits since the last revision:
> 
>  - Refactoring
>  - Remove convoluted native trace logic

src/hotspot/share/jfr/support/jfrThreadLocal.cpp line 587:

> 585: }
> 586: 
> 587: bool JfrThreadLocal::acquire_cpu_time_jfr_native_lock() {

It appears that the lock state 'NATIVE' is redundant; an asynchronous request for queue drainage only requires the dequeue lock state. NATIVE can be removed to simplify the lock protocol.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2119268003