RFR: 8328473: StringTable and SymbolTable statistics delay time to safepoint [v2]

[Coleen Phillimore]

On Mon, 24 Feb 2025 18:41:28 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> This change adds a safepoint poll to gathering statistics for the Symbol and String tables, using the ConcurrentHashTableTasks to chunk up the walk.  The stringTable and symbolTable is similar, like the GrowTask and DeleteTask code.  Maybe this can be cleaned up but I don't have a good idea about that yet that doesn't involve yet another level of templated functions and code. This is already pretty highly templatized.
>> Tested with tier1-4 and runThese internal test with JFR and failure injection to verify that we do try to safepoint while gathering statistics.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fxi typo.

Thanks for writing the experiment.  I can confirm that the times to safepoint after the patch don't have the long delays than the times before the patch, like:

[31.078s][info][safepoint  ] Safepoint "ParallelGCCollect", Time since last: 100220803 ns, Reaching safepoint: 116514226 ns, At safepoint: 56694466 ns, Total: 173208692 ns

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PR Comment: https://git.openjdk.org/jdk/pull/23750#issuecomment-2682939272