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

[William Kemper]

On Tue, 19 Nov 2024 17:31:15 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/shenandoahMarkingContext.cpp line 44:
> 
>> 42:   for (size_t idx = 0; idx < num_regions; idx++) {
>> 43:     ShenandoahHeapRegion* r = heap->get_region(idx);
>> 44:     if (r->is_affiliated() && heap->is_bitmap_slice_committed(r) && !is_bitmap_clear_range(r->bottom(), r->end())) {
> 
> I don't understand this for single gen mode. In that mode `is_affiliated() == false` always, right? So this check never passes, and `is_bitmap_clear` always returns `true`?

No, in single gen mode regions that are not `FREE` are affiliated with `YOUNG`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21273#discussion_r1849165775