RFR: Add generations to freeset [v23]

Mon May 1 23:00:09 UTC 2023

On Mon, 1 May 2023 22:10:00 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> ShenandoahFreeSet has not yet been modified to deal efficiently with the combination of old-gen and young-gen collection set reserves.  This PR makes changes so that we can distinguish between collector_is_free, old_collector_is_free, and mutator_is_free.  Further, it endeavors to keep each set of free regions tightly packed, so the range of regions representing each set is small.
>> 
>> In its current form, this no longer fails existing regression tests (except for known problems that are being addressed independently)
>
> Kelvin Nilsen has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Reviewer feedback: fix capitalization in comment
>  - Reviewer feedback: add a TODO comment

Marked as reviewed by wkemper (Committer).

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PR Review: https://git.openjdk.org/shenandoah/pull/250#pullrequestreview-1408202921