RFR: 8327000: GenShen: Integrate updated Shenandoah implementation of FreeSet into GenShen [v8]

[Kelvin Nilsen]

On Wed, 19 Jun 2024 18:11:08 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> Thanks for asking these questions and digging into the details.  I see in your other comment that it is the intention that we only increment gc_no_progress_count for consecutive full GCs.  However, our implementation seems to have drifted from that intention.  We also increment following a degen that does not make progress.  And then we increment again in the Full GC after we upgrade to full.  Maybe there are better ways to fix this.  I'm investigating.
>
> I'm of the "opinion" that consecutive Full GC failures means no intervening successful concurrent or degenerated collections.

I'm proposing two changes:
1. Do not increment gc_no_progress in failed degens
2. Reset gc_no_progress to zero after successful concurrent gc

I will remove this comment, and I will test this change.  I believe this may allow me to backoff the extreme testing overrides of ShenandoahNoProgressThreshold.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/440#discussion_r1646580580