RFR: 8290966: G1: Record number of PLAB filled and number of direct allocations

[Sangheon Kim]

On Mon, 25 Jul 2022 14:11:24 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   for evaluation in [JDK-8288966](https://bugs.openjdk.org/browse/JDK-8288966) I added statistics output that show the amount of PLAB fills and direct allocations; I think this is useful for similar evaluations in the future, so I kept and split it out from that change. Adds these values to the existing JFR event too.
> 
> Testing: PLAB related tests, gha
> 
> Thanks,
>   Thomas

Lgtm.

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Marked as reviewed by sangheki (Reviewer).

PR: https://git.openjdk.org/jdk/pull/9626