RFR: Allow young collection to suspend marking in old generation [v3]

[earthling-amzn]

On Fri, 26 Feb 2021 19:43:53 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> This looks much better! My tests now die when attempting full-GC, which is expected (and not going to be addressed in this PR). hotspot_gc_shenandoah also seems stable now. I'll give it an in-depth review next week.
>
> You should enable GitHub actions in your fork under Settings->Actions->Allow all actions. Then you'll get presubmit-tests which runs a whole bunch of stuff on various platforms. A great sanity check.

Yes, it's looking much more stable now. Hmm, I have actions enabled and I see it running builds on different platforms. I've been abusing this branch/pull request to fix windows and aarch64 builds.

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PR: https://git.openjdk.java.net/shenandoah/pull/19