RFR: 8368152: Shenandoah: Incorrect behavior at end of degenerated cycle [v4]

[William Kemper]

On Tue, 23 Sep 2025 22:24:14 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> There are several issues addressed in this PR:
>> * Shenandoah always ran a full GC after any degenerated cycle
>> * The number of consecutive degenerated GCs with bad progress was reset for every degenerated cycle
>> * Good progress was reported in generational mode even when no progress is made
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Improve comments and names

You're right that the `generation` argument to `is_good_progress` is unused. I think it makes sense to instead pass this to the `shMetrics` constructor and have it evaluate `used` from the generation. I will experiment with this, but I think it's outside the scope of this PR.

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PR Comment: https://git.openjdk.org/jdk/pull/27456#issuecomment-3325736835