RFR: 8280579: Shenandoah: Skip regions in the back of sorted array when choosing cset [v2]

[Yude Lin]

> Can I have review on this small change that skips some unnecessary work in cset choosing?
> 
> When choosing regions to add to cset, we sort the regions from most garbage to least garbage. We then iterate the sorted array. We can break early from the loop if we find a region with (garbage <= garbage_threshold). Because we know the regions left won't have enough garbage and won't be added anyway.

Yude Lin has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'openjdk:master' into JDK-8280579
 - 8280579: Shenandoah: Skip regions in the back of sorted array when choosing cset

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7211/files
  - new: https://git.openjdk.java.net/jdk/pull/7211/files/5b6738c2..cfa75958

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7211&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7211&range=00-01

  Stats: 11257 lines in 643 files changed: 7224 ins; 2232 del; 1801 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7211.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7211/head:pull/7211

PR: https://git.openjdk.java.net/jdk/pull/7211