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

[Robbin Ehn]

On Mon, 5 Sep 2022 13:41:31 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> Please consider, only implemented on x64/aarch64 linux/windows.
>> 
>> On my box calling clock_gettime via JNI goes from 35ns to 28ns when enabled.
>> 
>> Passes t1-7 with option forced on, also passes t1-4 as is in this PR.
>
> Nice to see usage of this OS feature. I like it more than the serialization page we have in 11u (with `-XX:-UseMembar`) and Critical JNI Natives (which still have some advantage). I have observed the same speedup for a trivial JNI call on my x86_64 machine.

Thanks for having a look Martin(@TheRealMDoerr), I'll see what I can do regarding the define!

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