RFR: 8373225: GenShen: More adaptive old-generation growth heuristics [v3]

[Kelvin Nilsen]

On Tue, 9 Dec 2025 03:12:37 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> When old-gen consumes a small percentage of heap size, trigger when old-gen expands by more than ShenandoahMinOldGenGrowthPercent, with default value 50%, from the live data in old at time of previous old-gen mark.
>> 
>> When old-gen consumes a larger percentage of heap size, we trigger when old-gen expands by more than  ShenandoahMinOldGenGrowthRemainingHeapPercent, with default value 25%, of the memory not live in old at the last marking of old.
>
> Kelvin Nilsen has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 12 additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'jdk/master' into more-adaptive-old-triggers-gh
>  - Add comment to describe behavior of adjust_old_garbage_threshold()
>  - Simplify representation of growth percentages
>  - Change default value of ShenandoahMinOldGenGrowthRemainingHeapPercent
>  - make old evac ratio adaptive
>  - Merge remote-tracking branch 'jdk/master' into more-adaptive-old-triggers
>  - change default value of ShenandoahMinOldGenGrowthRemainingHeapPercent
>  - Merge remote-tracking branch 'jdk/master' into more-adaptive-old-triggers
>  - Adjust test for new defaults
>  - Merge remote-tracking branch 'jdk/master' into more-adaptive-old-triggers
>  - ... and 2 more: https://git.openjdk.org/jdk/compare/92ea7c4d...c7c22974

I reran the performance results following changes suggested by reviewers with similar results:
<img width="2185" height="191" alt="image" src="https://github.com/user-attachments/assets/c6f13150-f946-4065-b902-45c260357951" />

-------------

PR Comment: https://git.openjdk.org/jdk/pull/28561#issuecomment-3633865135