RFR: 8365880: Shenandoah: Unify memory usage accounting in ShenandoahFreeSet [v35]

[William Kemper]

On Fri, 31 Oct 2025 01:09:32 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> This PR eliminates redundant bookkeeping that had been carried out by both ShenandoahGeneration and ShenandoahFreeSet.  In the new code, we keep a single tally of relevant information within ShenandoahFreeSet.
>> Queries serviced by ShenandoahGeneration are now delegated to ShenandoahFreeSet.
>> 
>> This change eliminates rare and troublesome assertion failures that were often raised when the ShenandoahFreeSet tallies did not match the ShenandoahGeneration tallies.  These assertion failures resulted because the two sets of books are updated at different times, using different synchronization mechanisms.
>> 
>> The other benefit of this change is that we have less synchronization overhead because we only have to maintain a single set of books.
>
> Kelvin Nilsen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 157 commits:
> 
>  - Merge remote-tracking branch 'jdk/master' into freeset-has-authoritative-tallies
>  - Merge remote-tracking branch 'jdk/master' into freeset-has-authoritative-tallies
>  - reviewer feedback
>  - Merge remote-tracking branch 'jdk/master' into freeset-has-authoritative-tallies
>  - Rework implementation of CompressedClassSpaceSizeInJmapHeap.java
>  - fix errors in CompressedClassSpaceSizeInJmapHeap.java
>  - Add debug instrumentation to CompressedClassSpaceSizeInJmapHeap.java
>  - Add sleep to CompressedClassSpaceSizeInJmapHeap.java test
>  - Fix up vmstructs and other infrastructure for jmap heap dump
>  - After initialization, check for SoftMaxHeapSize changed by constraints enforcement
>  - ... and 147 more: https://git.openjdk.org/jdk/compare/6347f10b...53af6b19

Marked as reviewed by wkemper (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/26867#pullrequestreview-3406038405