RFR: 8271579: G1: Move copy before CAS in do_copy_to_survivor_space [v3]

[Nick Gasson]

On Fri, 6 Aug 2021 02:15:55 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Propose to move copy before CAS in do_copy_to_survivor_space, as we found this will improve G1 performance. Specjbb shows 3.7% in critical on aarch64, no change in max.
>> 
>> After this change copy_to_survivor in G1 is also aligned with PS's copy_to_survivor.
>
> Hamlin Li has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.

What type of machine are you using to get that result? We tested SPECjbb on AWS M6g but couldn't see any significant difference in critical jops.

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PR: https://git.openjdk.java.net/jdk/pull/4983