RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v58]

[Johannes Bechberger]

On Wed, 4 Jun 2025 18:53:35 GMT, Andrei Pangin <apangin at openjdk.org> wrote:

>> Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Improve disenroll
>
> src/hotspot/share/jfr/periodic/sampling/jfrSampleRequest.cpp line 333:
> 
>> 331:     }
>> 332:   }
>> 333:   request._sample_ticks = JfrTicks::now();
> 
> For accurate correlation with other events, timestamp of a sample should be taken as early as possible, preferably in the beginning of `JfrCPUSamplerThread::handle_timer_signal`

I moved it up:


void JfrCPUSamplerThread::handle_timer_signal(siginfo_t* info, void* context) {
  JfrTicks now = JfrTicks::now();

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PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2127294191