RFR: 8337815: Relax G1EvacStats atomic operations

Fri Aug 9 17:58:58 UTC 2024

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.

-------------

Commit messages:
 - 8337815: Relax G1EvacStats atomic operations

Changes: https://git.openjdk.org/jdk/pull/20529/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20529&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337815
  Stats: 7 lines in 1 file changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/20529.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20529/head:pull/20529

PR: https://git.openjdk.org/jdk/pull/20529