RFR: 8337511: Implement JEP 404: Generational Shenandoah (Experimental) [v7]

[William Kemper]

On Fri, 15 Nov 2024 14:05:51 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> William Kemper has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 510 commits:
>> 
>>  - Merge branch 'merge-latest' into great-genshen-pr-redux
>>  - Use new CompactHeader forwarding APIs in generational mode
>>  - Merge remote-tracking branch 'jdk/master' into merge-latest
>>  - Merge
>>  - 8343649: Shenandoah: ShenandoahEvacInfo event does not follow JFR guidelines
>>    
>>    Reviewed-by: wkemper
>>  - Merge
>>  - 8343227: GenShen: Fold resource mark into management of preselected regions
>>    
>>    Reviewed-by: kdnilsen
>>  - Merge openjdk/jdk tip into great-genshen-pr-redux
>>  - Merge remote-tracking branch 'jdk/master' into merge-latest
>>  - Merge remote-tracking branch 'jdk/master' into merge-latest
>>  - ... and 500 more: https://git.openjdk.org/jdk/compare/889f9062...5e02b5d8
>
> src/hotspot/share/gc/shenandoah/shenandoahGenerationalHeap.cpp line 276:
> 
>> 274:             // where abundance is defined as >= ShenGenHeap::plab_min_size().  In the former case, we try shrinking the
>> 275:             // desired PLAB size to the minimum and retry PLAB allocation to avoid cascading of shared memory allocations.
>> 276:             if (plab->words_remaining() < plab_min_size()) {
> 
> Sonar caught it: There is a `plab != nullptr` check above at L267, which implies `plab` can be `nullptr` here? This would SEGV.

https://bugs.openjdk.org/browse/JDK-8344320

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PR Review Comment: https://git.openjdk.org/jdk/pull/21273#discussion_r1844209761