RFR: 8037914: Add JFR event for string deduplication [v6]

[Erik Gahlin]

On Thu, 6 Nov 2025 01:59:41 GMT, Francesco Andreuzzi <fandreuzzi at openjdk.org> wrote:

>> In this PR I introduce a new JFR event: `jdk.StringDeduplication`
>> 
>> The new event is emitted every time a deduplication cycle happens.
>> 
>> Passes tier1 and tier2 (fastdebug).
>
> Francesco Andreuzzi has updated the pull request incrementally with one additional commit since the last revision:
> 
>   rename. start/end time

This looks better, but I think activeElapsed can be removed since we now have it in duration. I'm not sure idle should be included, unless it is believed to be important.


activeElapsed = 0.00124 ms
processElapsed = 0.00100 ms
idleElapsed = 0.000780 ms
resizeTableElapsed = 0 s
cleanupTableElapsed = 0 s


An argument can be made that the phases should be separate events, similar to CompilerPhase and GCPausePhase, where you have a name for each phase (String Processing, Table Resize and Table Cleanup), but it may be over-engineering if we don't believe these phases will change in the future? The suffix "Elapsed" is not something we have used for describing a timespan. I wonder if the fields should be:

processing
tableResize
tableCleanup

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PR Comment: https://git.openjdk.org/jdk/pull/28015#issuecomment-3510740806