RFR: 8277930: Add unsafe allocation event to jfr [v5]

[Denghui Dong]

On Wed, 1 Dec 2021 14:43:50 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> Maybe it's an idea to implement these events in Java code instead? (using the JFR mirror events). I think the overhead should always be zero if the events are disabled in that case, right?

In my opinion, these events will be enabled when direct memory leak occurs during application running. In other words, users will not enable them at startup. 

So if these events are implemented by Java layer, some methods will be deoptimized which causes performance degradation of the application for a period of time if I understand correctly.

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PR: https://git.openjdk.java.net/jdk/pull/6591