RFR: 8327000: GenShen: Integrate updated Shenandoah implementation of FreeSet into GenShen [v8]

[William Kemper]

On Thu, 13 Jun 2024 22:22:01 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> The mainline implementation of ShenandoahFreeSet was recently updated.  This PR integrates the upstream changes
>> into Generational Shenandoah.
>
> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Minor refinements to test programs
>   
>   TestAllocIntArrays: comments to explain behavior.
>   TestOldGrowthTriggers: reduce the number of loop iterations so this test
>   will not time out on less powerful test platforms.

Minor suggestions. I think it will be easier to compare the freeset changes here with upstream (i.e., openjdk:master).

src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp line 138:

> 136:          if (is_old()) {
> 137:            heap->old_generation()->decrement_affiliated_region_count();
> 138:            heap->old_generation()->decrease_capacity(region_size_bytes());

Should capacity be updated every time affiliated region count changes? If yes, then we could have increase/decrease affiliated region count increase/decrease capacity directly. If no, is this something peculiar to full GC?

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

Changes requested by wkemper (Committer).

PR Review: https://git.openjdk.org/shenandoah/pull/440#pullrequestreview-2123863941
PR Review Comment: https://git.openjdk.org/shenandoah/pull/440#discussion_r1643406703