RFR: 8292266: Add JFR event for total Reference processing time [v6]

[Albert Mingkun Yang]

On Tue, 22 Nov 2022 07:21:39 GMT, Sangheon Kim <sangheki at openjdk.org> wrote:

>> Hi all,
>> 
>> Can I have reviews for this change that adds a new JFR event for total Reference Processing time?
>> 
>> The goal is to generate a new JFR event if there is already measured time. This CR doesn't add new time measurement.
>> 
>> Testing: hs-tier1 ~ 3
>> 
>> Thanks,
>> Sangheon
>
> Sangheon Kim has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rename to report_gc_reference_processing_time(). Change test @requires to !=Epsilon.

I think the new event for ref-processing time should be roughly corresponding to its neighbor `<Event name="GCReferenceStatistics"` in `metadata.xml`, regardless of ref-processing being STW or not.

> When/if we add concurrent reference processing time tracking (which isn't trivial to do)

@sangheon 's latest revision does that for Shenandoah and Z.

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PR: https://git.openjdk.org/jdk/pull/11230