RFR: 8275055: Improve HeapRegionRemSet::split_card() [v5]

[Albert Mingkun Yang]

On Tue, 19 Oct 2021 14:12:20 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   can I have reviews for this small change that improves HeapRegionRemSet::split_card() by reducing the number of (direct and indirect) memory accesses for it. It is hard to actually measure improvements because it's only called in concurrent code. So no particular improvements measured.
>> 
>> It also prepares that method for virtualizing the remembered set containers, allowing arbitrarily large heap region sizes [JDK-8275056](https://bugs.openjdk.java.net/browse/JDK-8275056). This change is required then because the splitting of a card index into "region" and "card within region" should not be dependent on *heap regions*.
>> 
>> Testing: gha, gc/g1 local testing.
>> 
>> Thanks,
>>   Thomas
>
> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix windows compilation

`_heap_base_address` feels more natural to live in `G1CollectedHeap`. Anyway, this is very subjective.

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Marked as reviewed by ayang (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/5895