RFR: 8037914: Add JFR event for string deduplication

[Erik Gahlin]

On Wed, 29 Oct 2025 23:34:40 GMT, Francesco Andreuzzi <fandreuzzi at openjdk.org> wrote:

> Sure, I disabled the new event in `default.jfc`.

Best would be to have it enabled, but if you believe we could get a very high number of events, it must be disabled or emitted at a lower frequency.

Typically, statistical events are emitted as periodic events, so users can set the period, e.g. 10 s, but that would require synchronization, which could also create issues.

> `<setting name="enabled" control="gc-enabled-normal">false</setting>`

The control parameter must be in sync with the element value.
**gc-enabled-normal** is the default mode, which means it will be true. 

**gc-enabled-high**, **gc-enabled-detailed** and **gc-enabled-all** are false by default. 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.

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PR Comment: https://git.openjdk.org/jdk/pull/28015#issuecomment-3466243974