RFR: 8339162: [REDO] JDK-8338440 Parallel: Improve fragmentation mitigation in Full GC

Mon Nov 4 11:01:40 UTC 2024

This PR consists of two commits, the original and bug-fix.

The original patch calculates the dest-count for the preceding live words incorrectly -- `preceding_destination` can be on region-boundary.

Test: TEST=gc/TestSoftReferencesBehaviorOnOOME.java fails ~4/100 without the fix but passes with the fix.

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Commit messages:
 - fix
 - original

Changes: https://git.openjdk.org/jdk/pull/21872/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21872&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339162
  Stats: 568 lines in 2 files changed: 209 ins; 143 del; 216 mod
  Patch: https://git.openjdk.org/jdk/pull/21872.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21872/head:pull/21872

PR: https://git.openjdk.org/jdk/pull/21872