RFR: 8315149: Add hsperf counters for CPU time of internal GC threads [v8]

[Volker Simonis]

On Fri, 8 Sep 2023 21:40:26 GMT, Jonathan Joo <jjoo at openjdk.org> wrote:

>> 8315149: Add hsperf counters for CPU time of internal GC threads
>
> Jonathan Joo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix includes

Thanks for your changes. Already much better now, but I still have some comments :)

src/hotspot/share/gc/shared/stringdedup/stringDedupProcessor.cpp line 71:

> 69:     EXCEPTION_MARK;
> 70:     _concurrent_dedup_thread_cpu_time =
> 71:         PerfDataManager::create_counter(SUN_THREADS, "g1_conc_dedup_thread.cpu_time",

I think this counter is not G1 specific so please drop `g1_` from the name.

src/hotspot/share/runtime/vmThread.cpp line 299:

> 297:            "Must be called from VM thread");
> 298:     // Update vm_thread_cpu_time after each VM operation.
> 299:     // _perf_vm_thread_cpu_time->set_value(os::current_thread_cpu_time());

I don't think we need this comment line any more (and it is also wrong, now that we've changed the `PerfVariable` to a `PerfCounter`.

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Changes requested by simonis (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/15082#pullrequestreview-1620155306
PR Review Comment: https://git.openjdk.org/jdk/pull/15082#discussion_r1321646182
PR Review Comment: https://git.openjdk.org/jdk/pull/15082#discussion_r1321673421