RFR: 8373225: GenShen: More adaptive old-generation growth heuristics [v2]

[Kelvin Nilsen]

On Mon, 8 Dec 2025 16:32:53 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Kelvin Nilsen has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - Add comment to describe behavior of adjust_old_garbage_threshold()
>>  - Simplify representation of growth percentages
>>  - Change default value of ShenandoahMinOldGenGrowthRemainingHeapPercent
>
> src/hotspot/share/gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp line 212:
> 
>> 210:   void slide_pinned_regions_to_front();
>> 211:   bool all_candidates_are_pinned();
>> 212:   void adjust_old_garbage_threshold();
> 
> A brief general comment about the algorithm here or in the implementation would be welcome. As I read it, we are lowering the region's garbage threshold as the occupancy in the old generation increases. Lowering the garbage threshold will increase the number of old regions selected for a mixed collection.

Thanks.  I've added this description.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28561#discussion_r2600711259