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/support/jfrThreadLocal.hpp line 401:

> 399: 
> 400:   JfrCPUTimeTraceQueue& cpu_time_jfr_queue();
> 401:   void disable_cpu_time_jfr_queue();

Seems a bit strange that you can "disable" a queue. When is it enabled? Since the underlying implementation delegates to ensure_capacity for size == 0, and deallocates, perhaps a more appropriate name is "deallocate_cpu_time_jfr_queue()"?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2106313484