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

[Aleksey Shipilev]

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.

Sure, if you can trigger JFR events often programmatically, that would also work. Otherwise, the experimental change in `VM_DumpHashtable` is okay to prove out the statistics dumping code. We can do in _properly_ in a separate PR, but a quick hack is okay for performance tests.

I am really interested in TTSP figures from `-Xlog:safepoint` before/after this patch under heavy give-me-statistics requests.

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PR Comment: https://git.openjdk.org/jdk/pull/23750#issuecomment-2679404944