RFR: 8280783: Parallel: Refactor PSCardTable::scavenge_contents_parallel

Thu Jan 27 08:57:46 UTC 2022

A new version of `PSCardTable::scavenge_contents_parallel` with cleaner structure and most of the existing behavior. The deviation is so large that the diff is not very sensible; reading the new code directly is probably easier.

This PR doesn't take advantage of precise card marking, just like the existing code. IOW, the code assumes all cards are *imprecisely* marked. Optimizations like utilizing precise card marking will be investigated/attempted in another ticket/PR.

Test: Tier1-6

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Commit messages:
 - scavenge_contents_parallel

Changes: https://git.openjdk.java.net/jdk/pull/7243/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7243&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280783
  Stats: 277 lines in 2 files changed: 103 ins; 102 del; 72 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7243.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7243/head:pull/7243

PR: https://git.openjdk.java.net/jdk/pull/7243