RFR: 8294775: Shenandoah: reduce contention on _threads_in_evac [v4]

[Aleksey Shipilev]

On Tue, 11 Oct 2022 12:28:27 GMT, Nick Gasson <ngasson at openjdk.org> wrote:

>> src/hotspot/share/gc/shenandoah/shenandoahEvacOOMHandler.cpp line 55:
>> 
>>> 53:   // *and* the counter is zero.
>>> 54:   while (Atomic::load_acquire(ptr) != OOM_MARKER_MASK) {
>>> 55:     os::naked_short_sleep(1);
>> 
>> Not sure if SpinPause() may be better here? @shipilev probably knows more.
>
> I think we'd probably want some back-off here rather than spinning indefinitely? E.g. spin N times and then start sleeping.

This code does what old code did, and on that grounds it is fine to keep `naked_short_sleep`.

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PR: https://git.openjdk.org/jdk/pull/10573