RFR: 8273626: G1: refactor G1CardSetAllocator to support element size less pointer size

[Thomas Schatzl]

On Sat, 11 Sep 2021 05:05:47 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).

Hi Hamlin,

  just fyi, I am aware that this CR is out, but currently I am a too busy looking into nontrivial PRs with some pre/post-JDK17 GA work. Initial look seems good though.

Thomas

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