RFR: 8159979: During initial mark, preparing all regions for marking may take a significant amount of time [v2]

[Ivan Walulya]

> Hi all,
> 
> Please review this change to move preparing regions for marking to the multithreaded execution in G1PrepareEvacuationTask.
> 
> Testing: Tier 1-3.

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

  remove unrelated changes

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5251/files
  - new: https://git.openjdk.java.net/jdk/pull/5251/files/56f1ce15..37b29959

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5251&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5251&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5251.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5251/head:pull/5251

PR: https://git.openjdk.java.net/jdk/pull/5251