RFR: 8273626: G1: Factor out concurrent segmented array from G1CardSetAllocator [v3]

[Hamlin Li]

On Fri, 24 Sep 2021 08:37:30 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> To finish https://bugs.openjdk.java.net/browse/JDK-8254739, we need a segmented array to store a growing regions index array, in the initial version of that patch, a newly home made segmented array was used, but the memory efficiency is not as good as expected, G1CardSetAllocator is a potential candidate to fullfill the requirement, but need some enhancement.
>> 
>> This is a try to enhance G1CardSetAllocator(and G1CardSetBuffer, G1CardSetBufferList) to support element size less pointer size, and strip this basic function as a more generic segmented array (G1SegmentedArray).
>
> Hamlin Li has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into generalize-g1CardSetBuffer-and-Allocator
>  - Rename Xxx to G1Xxx
>  - Clean code
>  - Fix wrong length() in SegmentedArrayBuffer, cause it might grow more than _elem_nums
>  - Initial commit

Kindly reminder.

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PR: https://git.openjdk.java.net/jdk/pull/5478