RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v5]

[Markus Grönlund]

On Fri, 23 May 2025 21:20:39 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:
> 
>   Fix compilation

src/hotspot/share/jfr/jni/jfrJniMethod.cpp line 28:

> 26: #include "jfr/jfrEvents.hpp"
> 27: #include "jfr/periodic/sampling/jfrThreadSampler.hpp"
> 28: #include "jfr/periodic/sampling/jfrCPUTimeThreadSampler.hpp"

Include order.

src/hotspot/share/jfr/periodic/sampling/jfrCPUTimeThreadSampler.cpp line 355:

> 353: void JfrCPUTimeThreadSampler::sample_out_of_safepoint(JavaThread* thread) {
> 354:   assert(thread->jfr_thread_local() != nullptr, "invariant");
> 355:   JfrThreadLocal* tl = thread->jfr_thread_local();

Perhaps assert tl != nullptr here instead.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2106223669
PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2106223067