RFR: 8315149: Add hsperf counters for CPU time of internal GC threads [v18]

[Jonathan Joo]

On Wed, 11 Oct 2023 22:25:04 GMT, Man Cao <manc at openjdk.org> wrote:

>> src/hotspot/share/runtime/perfData.hpp line 64:
>> 
>>> 62:   COM_THREADS,
>>> 63:   SUN_THREADS,
>>> 64:   SUN_THREADS_GCCPU,    // Subsystem for Sun Threads GC CPU
>> 
>> Really not sure about this naming ...
>
> +1,  dropping the "GC" seems better, i.e. `SUN_THREADS_CPUTIME` and `sun.threads.cpu_time`. For example, `sun.threads.gc_cpu_time.vm` is strange since VM thread also does work unrelated to GC.
> 
> For @simonis's point about avoid duplicating the "g1" part in each counter's name, I think it is doable. How about the following list of names?
> 
> 
> sun.threads.total_gc_cpu_time    // Unchanged. Would sun.threads.cpu_time.gc_total look better?
> sun.threads.cpu_time.gc_parallel_workers
> sun.threads.cpu_time.gc_conc_mark
> sun.threads.cpu_time.gc_conc_refine
> sun.threads.cpu_time.vm
> sun.threads.cpu_time.conc_dedup
> 
> 
> `gc_conc_mark` and `gc_conc_refine` are currently tied to G1. It seems OK because these counters would not exist if G1 is not selected. If other collectors want to implement `gc_conc_mark` in the future, they could implement their own definition of this counter, or move G1's definition to a shared place.
> 
> @simonis does the list of names above look good to you?

Updated the counters for now to these names, but open to renaming again based on feedback from @simonis!

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PR Review Comment: https://git.openjdk.org/jdk/pull/15082#discussion_r1357639099