RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v38]

[Markus Grönlund]

On Tue, 3 Jun 2025 12:39:47 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:
> 
>   Restrict threads for which timers are created

src/hotspot/share/jfr/periodic/sampling/jfrThreadSampling.cpp line 479:

> 477: 
> 478: // Entry point for a thread that has been sampled in native code and has a pending JFR CPU time request.
> 479: void JfrThreadSampling::process_cpu_time_request(JavaThread* jt, JfrThreadLocal* tl, Thread* current, bool lock) {

Can you move this up to be co-located with  "drain_enqueued_cpu_time_requests"? Thanks.

src/hotspot/share/jfr/periodic/sampling/jfrThreadSampling.hpp line 40:

> 38:  public:
> 39:   static void process_sample_request(JavaThread* jt, bool has_cpu_time_sample_request);
> 40:   static void process_cpu_time_request(JavaThread* jt, JfrThreadLocal* tl, Thread* current, bool lock);

Put this under private and add JfrCPUTimeThreadSampler as a friend (like above with JfrSamplerThread and "process_native_sample_requests"

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

PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2123728400
PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2123726144