RFR: 8276129: PretouchTask should page-align the chunk size [v2]

[Kim Barrett]

> Please review this change to PretouchTask to page-align the chunk size.
> Aligning down is used because it's easy; aligning up would require dealing
> with possible overflow or verifying that overflow isn't possible.
> 
> Testing:
> mach5 tier1
> 
> Locally (linux-x64) java -version with pretouch task logging and various
> chunk sizes, manually verifying the number of workers was as expected.

Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:

  use align_down_bounded

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6204/files
  - new: https://git.openjdk.java.net/jdk/pull/6204/files/ee12018b..ce8ad82b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6204&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6204&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 3 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6204.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6204/head:pull/6204

PR: https://git.openjdk.java.net/jdk/pull/6204