RFR: 8351187: Add JFR monitor notification event

[Alan Bateman]

On Tue, 4 Mar 2025 16:05:36 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> We have `JavaMonitorWait` event, but no symmetric `JavaMonitorNotify` event. Notifications are important/interesting to track as well, for example to correlate the delay between notification and eventual wake up.
> 
> Providing this event would also replace one of of the RT counters that are going away in [JDK-8348829](https://bugs.openjdk.org/browse/JDK-8348829).
> 
> This counter is disabled by default to keep any potential impact low. We can consider flipping it to enabled by default later.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `jdk_jfr`

Do I read this correctly that this is a duration event and will only be recorded if the notify takes >= 10ms? When I read David's comment then I assumed it was an instant event but it seems not.  Given the "address" field then I assume this is intended to be part of a troubleshooting recipe, maybe with threshold set to 0ms, is that right?

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PR Comment: https://git.openjdk.org/jdk/pull/23901#issuecomment-2700083342