RFR: Expand old on demand [v42]

[Kelvin Nilsen]

On Wed, 24 May 2023 17:25:14 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> src/hotspot/share/gc/shenandoah/heuristics/shenandoahHeuristics.cpp line 104:
>> 
>>> 102: 
>>> 103: // Returns bytes of old-gen memory consumed by selected aged regions
>>> 104: size_t ShenandoahHeuristics::select_aged_regions(size_t old_available, size_t num_regions, bool preselected_regions[]) {
>> 
>> should probably call this preslected_region_candidates[]
>
> I'd prefer a name that described why these candidates are "pre-selected". Also not clear why these regions aren't added to the collection set through the same process as other regions.

I've changed the name of preselected_regions[] to candidate_regions_for_promotion_by_copy[].  I've also added a comment to explain (and motivate) the behavior of this function.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/248#discussion_r1205908284