RFR: 8264818: G1: Improve liveness check for empty pinned regions after full gc marking

[Hamlin Li]

On Wed, 14 Apr 2021 08:32:33 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   can I have reviews for this small change improving the check for empty Open Archive regions using information that has recently been added to the full gc in [JDK-8263495](https://bugs.openjdk.java.net/browse/JDK-8263495) instead of scanning the region?
> 
> Testing: tier1-3, manual check that the freeing still works using some hack to create a dummy Open Archive region which contents are completely unreferenced and then running a "Hello World" app doing a system.gc. The patch for the VM to create that archive is [here](https://github.com/openjdk/jdk/commit/47d740d244b09b104df635c07ee49f89f480ebc6).

looks good.

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Marked as reviewed by mli (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/3485