RFR: 8236176: Parallel GC SplitInfo comment should be updated for shadow regions [v2]

[Ivan Walulya]

> Hi all,
> 
> Please review this small change to add a high-level description of how shadow regions are utilized during the compact phase of the parallel GC. There is no special handling of Splitinfo by the shadow regions; the destination computation and the handling of partial_objects are done during the summary phase while the shadow regions optimization only applies to compaction. 
> 
> Additionally, some unused variables are cleaned up.

Ivan Walulya has updated the pull request incrementally with one additional commit since the last revision:

  Thomas review

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5195/files
  - new: https://git.openjdk.java.net/jdk/pull/5195/files/52fbb6fa..b394ba83

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5195&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5195&range=00-01

  Stats: 8 lines in 1 file changed: 0 ins; 1 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5195.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5195/head:pull/5195

PR: https://git.openjdk.java.net/jdk/pull/5195