RFR: 8292591: Experimentally add back barrier-less Java thread transitions [v5]

[Robbin Ehn]

On Fri, 9 Sep 2022 16:31:30 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

> Looks good to me! I think we can avoid always emitting the memory barrier for the JFR sampler if we move it inside the thread_state_in_native() case and then re-read the state after the barrier.

Thanks! If we can make the sampler performance better when using sysmembar it would be good.

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PR: https://git.openjdk.org/jdk/pull/10123