RFR: 8293650: Shenandoah: Support archived heap objects [v2]

[Aleksey Shipilev]

On Tue, 13 Aug 2024 16:34:00 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Move constant to separate class to unbreak Windows builds
>
> src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp line 2540:
> 
>> 2538: 
>> 2539:   // If the trailing region is not full, we need to adjust its top.
>> 2540:   size_t tail = (size % ShenandoahHeapRegion::region_size_words());
> 
> Not sure we need this. The free set adjusts top for all humongous regions in the allocation (including the tail): https://github.com/openjdk/jdk/blob/master/src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp#L885. What's more, I believe `new_top` is only used during a full GC to sort out `top` once compaction is complete.

Right, d'oh. Not sure what I was thinking there. I'll drop the block, since the whole thing apparently works without adjusting the top.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/20468#discussion_r1715823681