RFR: 8297692: Avoid sending per-region GCPhaseParallel JFR events in G1ScanCollectionSetRegionClosure

[Thomas Schatzl]

Hi all,

  please review this change that significantly reduces the amount of "Code Roots" and "Optional Roots" JFR events to reduce default recording sizes significantly.

E.g. a 10min BigRamTester run creates a 23MB recording without this change, with like hundreds of thousands of these events (#gcs * #gc threads * #regions in collection set). With this change, the recording is reduced to 4MB (#gcs * #gc threads)

Testing: gha, tier1-3

Thanks,
  Thomas

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Commit messages:
 - Update src/hotspot/share/gc/g1/g1RemSet.cpp
 - 8297692

Changes: https://git.openjdk.org/jdk/pull/21984/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21984&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297692
  Stats: 162 lines in 3 files changed: 84 ins; 52 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/21984.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21984/head:pull/21984

PR: https://git.openjdk.org/jdk/pull/21984