RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v27]

[Markus Grönlund]

On Mon, 2 Jun 2025 11:32:27 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:
> 
>  - Tiny fixes
>  - Minor changes

src/hotspot/share/runtime/thread.hpp line 59:

> 57: class SafeThreadsListPtr;
> 58: class ThreadClosure;
> 59: class ThreadCrashProtection;

Should not be needed.

src/jdk.jfr/share/classes/jdk/jfr/internal/JVM.java line 276:

> 274:      * Set the maximum event emission rate for the CPU time sampler
> 275:      *
> 276:      * Setting rate to 0 turns off the CPU time method sampler.

"CPU time method sampler" -> "CPU time sampler"

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2120878701
PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2120882161