RFR: 8276098: Do precise BOT updates in G1 evacuation phase

[Stefan Johansson]

On Mon, 1 Nov 2021 09:34:16 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

> Another thought is maybe `G1BlockOffsetTable::set_offset_array/_raw` don't need to be conservatively ordered, that is, they can be memory_order_relaxed. Since now all updates are in the pause and there is no concurrent readers.

Took a closer look at `G1BlockOffsetTable::set_offset_array/_raw`, it uses `Atomic::store(...)` and if I'm not mistaken that will not be "conservatively ordered".

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PR: https://git.openjdk.java.net/jdk/pull/6166