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

[Johannes Bechberger]

On Tue, 3 Jun 2025 21:42:48 GMT, Markus Grönlund <mgronlun 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/periodic/sampling/jfrCPUTimeThreadSampler.cpp line 520:
> 
>> 518:   // the sampling period might be too low for the current Linux configuration
>> 519:   // so samples might be skipped and we have to compute the actual period
>> 520:   int64_t period = get_sampling_period() * (info->si_overrun + 1);
> 
> Does this calculation have to be done on every signal, by every thread? It seems like something that could be precalculated when the period is set?

This might change dynamically, so probably no. Only caching would work, but this is a small optimization for later.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2125725230