RFR: 8342818: Implement JEP 509: JFR CPU-Time Profiling [v45]
Johannes Bechberger
jbechberger at openjdk.org
Wed Jun 4 11:28:54 UTC 2025
On Wed, 4 Jun 2025 11:23:57 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:
>> Johannes Bechberger has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 127 commits:
>>
>> - Merge branch 'master' into parttimenerd_cooperative_cpu_time_sampler
>> - Add error message on signal handler install failure
>> - Fix signal handler synchronization
>> - Improve
>> - Rename autoadapt
>> - Make process_cpu_time_request private and move up
>> - Reorder condition
>> - Tiny refactoring
>> - Restrict threads for which timers are created
>> - Fix tiny mistake
>> - ... and 117 more: https://git.openjdk.org/jdk/compare/7838321b...4fd4b673
>
> src/hotspot/share/jfr/periodic/sampling/jfrCPUTimeThreadSampler.cpp line 647:
>
>> 645: // install sig handler for sig
>> 646: if ((s8)PosixSignals::install_generic_signal_handler(SIG, (void*)::handle_timer_signal) == -1) {
>> 647: log_error(jfr)("Failed to install signal handler for CPU thread sampling, possibly because another profiler is active: %s", os::strerror(os::get_last_error()));
>
> That we are using a signal handler to provide the user with CPU time information is an implementation detail. Its good to provide an error message, but I think it should reflect back on something the user is expecting.
>
> Perhaps add a line that says something along the lines of "CPUTimeSample events will not be recorded."
Done
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/25302#discussion_r2126360801
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