RFR: 8315149: Add hsperf counters for CPU time of internal GC threads [v48]

[Stefan Johansson]

On Tue, 28 Nov 2023 02:22:45 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 two additional commits since the last revision:
> 
>  - Fix namespace issues (2)
>    
>    Co-authored-by: Stefan Johansson <54407259+kstefanj at users.noreply.github.com>
>  - Fix namespace issues
>    
>    Co-authored-by: Stefan Johansson <54407259+kstefanj at users.noreply.github.com>

>From a testing point of view I think this is looking good now, re-ran the failing test and some other jstat tests as well and they all pass.

Please address the comments from Albert and we can hopefully finish this before RDP1.

src/hotspot/share/runtime/cpuTimeCounters.cpp line 91:

> 89:   } while (old_value != fetched_value);
> 90:   get_counter(CPUTimeGroups::CPUTimeType::gc_total)->inc(fetched_value);
> 91: }

Why do we have to do this publish dance? Couldn't the closure that update the diff instead just update the counter? From what I can tell we never have multiple closures active at the same time so should be no race there?

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PR Review: https://git.openjdk.org/jdk/pull/15082#pullrequestreview-1754686415
PR Review Comment: https://git.openjdk.org/jdk/pull/15082#discussion_r1408914724