RFR: 8037914: Add JFR event for string deduplication

[Erik Gahlin]

On Sat, 1 Nov 2025 11:45:27 GMT, Francesco Andreuzzi <fandreuzzi at openjdk.org> wrote:

> > It would be good if you could provide some ballpark figures on the number of events in a worst-case scenario, so we can determine what GC level is appropriate.
> 
> I wrote a simple pathological test with multiple threads interning random strings, [this](https://github.com/user-attachments/files/23282465/out-parallel.txt) is the worst I've seen: 100 deduplication rounds within `3.698s` and `3.729s`.

Thanks for investigating this. It doesn't sound that bad, the event could probably be enabled by default. The elapsed fields, are they the total since the JVM started or from the last round?

We typically try to avoid using "Bytes" in field names, since that information is already available in the content type. Perhaps something else could be used, newSize?

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PR Comment: https://git.openjdk.org/jdk/pull/28015#issuecomment-3481567424