RFR: 8269870: PS: Membar in PSPromotionManager::copy_unmarked_to_survivor_space could be relaxed

[Hamlin Li]

On Mon, 12 Jul 2021 02:43:29 GMT, Hamlin Li <mli at openjdk.org> wrote:

> Membar in PSPromotionManager::copy_unmarked_to_survivor_space could be relaxed.
> ( Please also refer to the similar membar relaxed in G1ParScanThreadState::do_copy_to_survivor_space )
> 
> Per the specjbb2015 test results, it has about 8% improvement in critical.
> https://bugs.openjdk.java.net/secure/attachment/95445/jdk17_default_options.v2.png

I thought it's because of some log message in PS which needs to refer to forwardee's content, and the log messages is now gone.
But let me do a more comprehensive investigation, will update later.

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PR: https://git.openjdk.java.net/jdk/pull/4751