RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v42]

[Johannes Bechberger]

On Wed, 4 Jun 2025 00:28:46 GMT, Andrei Pangin <apangin at openjdk.org> wrote:

>> Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Rename autoadapt
>
> src/hotspot/share/jfr/support/jfrThreadLocal.cpp line 558:
> 
>> 556: void JfrThreadLocal::set_cpu_timer(timer_t* timer) {
>> 557:   if (_cpu_timer == nullptr) {
>> 558:     _cpu_timer = JfrCHeapObj::new_array<timer_t>(1);
> 
> `timer_t` is a primitive type, at most one machine word. Why extra indirection and allocation?

@mgronlun wanted this indirection to move it abstract from implementation details

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2125758074