RFR: 8296954: G1: Enable parallel scanning for heap region remset [v2]

[Albert Mingkun Yang]

On Mon, 28 Nov 2022 08:34:37 GMT, Ivan Walulya <iwalulya at openjdk.org> wrote:

>> Hi all, 
>> 
>> Please review this change that allows parallel scanning of a heap region's remembered set.  More balanced work load distribution in cases where are cards are unevenly distributed among remembered sets.
>> 
>> Testing: Tier 1-3
>> 
>> Thanks
>
> Ivan Walulya has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Thomas review

I believe some performance results (benchmark setup, what metric is improved, etc) should be posted on the corresponding JBS ticket to better motivate this feature. The change looks fine.

src/hotspot/share/gc/g1/g1CardSet.cpp line 246:

> 244:   using CHTScanTask = CardSetHash::ScanTask;
> 245: 
> 246:   const static uint BucketClaimSize = 16;

Some comment on how `16` is derived would be nice and probably useful for future re-evaluation.

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Marked as reviewed by ayang (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11173