RFR: 8339097: Parallel: Compact GC to split array early for task stealing

[Zhengyu Gu]

Parallel Compact GC splits a large array in stripes during marking, so that other workers can steal the work.

Currently, it only splits a large array into two tasks, retains and pushes remaining into a task queue for task stealing, depends on next worker to further split the array if possible, that creates artificial dependency.

I would like purpose to have the first worker breaking up the array, to eliminate the dependency.

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

Commit messages:
 - 8339097: Parallel: Compact GC to split array early for task stealing

Changes: https://git.openjdk.org/jdk/pull/20745/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20745&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339097
  Stats: 8 lines in 1 file changed: 4 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20745.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20745/head:pull/20745

PR: https://git.openjdk.org/jdk/pull/20745