RFR: 8375643: G1: Convert G1RegionMarkStatsCache to use Atomic<T>

[Kim Barrett]

On Mon, 19 Jan 2026 16:56:09 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change to make `G1RegionMarkStatsCache` use `Atomic<T>`.
> 
> The only unusual part is that I added two getters to that class to avoid the repeated `.load_relaxed()` typing.
> 
> Testing: gha
> 
> Thanks,
>   Thomas

Looks good.

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Marked as reviewed by kbarrett (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/29303#pullrequestreview-3679205978