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

[Ivan Walulya]

> 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

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11173/files
  - new: https://git.openjdk.org/jdk/pull/11173/files/b0891932..358e550a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11173&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11173&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11173.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11173/head:pull/11173

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