RFR: 8373225: GenShen: More adaptive old-generation growth heuristics [v5]

[Kelvin Nilsen]

On Thu, 11 Dec 2025 00:48:58 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp line 90:
>> 
>>> 88:           "ShenandoahGenerationalDoNotIgnoreGrowthAfterYoungCycles "        \
>>> 89:           "consecutive cycles have been completed following the "           \
>>> 90:           "preceding old-gen collection.")                                  \
>> 
>> Here again, like my remark below, we can effectively decouple the two options and simplify the verbage by merely saying:
>> 
>> 
>> // Do not use Old generation growth as a triggering criterion
>> // when usage is lower than this percentage of heap.
>> 
>> 
>> I am not sure if "of heap" is correct, or if there is some other implicit percentage of the old generation capacity that one has in mind here.
>
> As I read the code for the old heuristic growth trigger, I realize my rewording above is incorrect.
> 
> I think the code in the triggering could be simplified a bit to allow a more crisp description of these parameters.
> 
> Let me talk with you offline (face to face).

Sounds good.  I'm inclined to leave these behaviors as is for now.  These are not the focus of this particular PR.  But let's think about creating a new JBS ticket and PR to improve further if that's ok.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28561#discussion_r2611288502