RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v29]

[Johannes Bechberger]

On Mon, 2 Jun 2025 14:57:22 GMT, Johannes Bechberger <jbechberger at openjdk.org> wrote:

>> src/hotspot/share/jfr/periodic/sampling/jfrCPUTimeThreadSampler.cpp line 349:
>> 
>>> 347:   const frame top_frame = thread->last_frame();
>>> 348:   bool in_continuation = is_in_continuation(top_frame, thread);
>>> 349:   for (u4 i = 0; i < queue.size(); i++) {
>> 
>> Realized this drainage is entirely wrong!
>> 
>> You are not using the sample requests in the queue to build individual stack traces for events; instead, you are using the same top frame (the last Java frame) for all of them.
>
> Can I export compute_top_frame and use it here?

Or just create a `Jfr::drain_cpu_time_queue` method?

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

PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2121426469