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 the work done during preparation for a concurrent mark start (pre_concurrent_start) into a G1BatchedGangTask.
> 
> Testing: Tier 1-3

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

  typo

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5302/files
  - new: https://git.openjdk.java.net/jdk/pull/5302/files/19a33196..f7db3b1b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5302&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5302&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5302.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5302/head:pull/5302

PR: https://git.openjdk.java.net/jdk/pull/5302