Withdrawn: 8273122: ZGC: Load forwarding entries without acquire semantics

[duke]

On Mon, 30 Aug 2021 09:17:12 GMT, Hao Tang <duke at openjdk.java.net> wrote:

> JDK-8272138 introduced an unbound membar release() between the object copy and the forwarding table insertion.
> 
> Thread A (Relocation):
> copy();
> release();
> cas_forwarding_table();
> cas_self_heal();
> 
> The membar guarantees that the contents of the forwarded object are ready after a forwarding entry is loaded. Since load_object_content(ref) depends on the result of load_forwarding_table(), load_acquire can be safely changed to a simple load.
> 
> Thread B (Remapping/Relocation):
> ref = load_forwarding_table(); // acquire (current version) -> relaxed (our proposal)
> load_object_content(ref);
> 
> Our experiment on heapothesys demonstrates >5% time reduction spent on concurrent mark/relocation on AArch64.
> 
> ---------
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This pull request has been closed without being integrated.

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PR: https://git.openjdk.java.net/jdk/pull/5298