RFR: 8337815: Relax G1EvacStats atomic operations

[Aleksey Shipilev]

On Fri, 9 Aug 2024 17:46:43 GMT, Ben Taylor <btaylor at openjdk.org> wrote:

> This PR should slightly improve the performance of G1EvacStats by using `memory_order_relaxed` instead of the default `memory_order_conservative`.
> Since the original bug report says
> 
>>I doubt it would show on benchmarks, this is a paper-cut issue.
> 
> I haven't benchmarked this change for performance.
> 
> The change passes all tests in `gc/g1` locally on x86_64 linux.

Marked as reviewed by shade (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/20529#pullrequestreview-2232324912