[jdk21u-dev] RFR: 8314573: G1: Heap resizing at Remark does not take existing eden regions into account

[Liang Mao]

Clean backport of fix of G1 Heap resizing heuristics at remark

Additional testing:
 - [x] Linux aarch64 server release/fastdebug, test/hotspot/jtreg/gc with +UseG1GC

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Commit messages:
 - Backport 762b652912939b37fbd68955617705c62b9fc3a5

Changes: https://git.openjdk.org/jdk21u-dev/pull/429/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=429&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314573
  Stats: 8 lines in 1 file changed: 7 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/429.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/429/head:pull/429

PR: https://git.openjdk.org/jdk21u-dev/pull/429