RFR: DRAFT: Expand old on demand [v3]

[Kelvin Nilsen]

On Sat, 8 Apr 2023 23:09:33 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> This PR describes several proposed changes to dynamically adjust the sizes of old-gen and young-gen.  In general, the objective is to keep old-gen as small as possible so that there is an abundance of memory available for the young-gen allocation runway.
>> 
>> As currently drafted, there are regression failures.  This DRAFT PR is published for the purpose of facilitating a careful code review.
>
> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Polish to facilitate code reviews
>   
>   Reorder some code so that it better matches original organization.
>   Cleanup comments.

src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp line 190:

> 188:           continue;
> 189:         }
> 190:         if  (r->age() < InitialTenuringThreshold) {

why am i not checking for !r->is_old().  investigate.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/248#discussion_r1161170979