[jdk11u-dev] RFR: 8228609: G1 copy cost prediction uses used vs. actual copied bytes

[Yude Lin]

I would like to backport 8228609 which fixes a prediction error regarding cost per bytes copied.

The patch does not apply cleanly, so this backport is basically changing the calculation of copied bytes.

https://bugs.openjdk.java.net/browse/JDK-8227442 is not in 11u. So this patch also uses G1ParScanThreadState::surviving_young_words() in place of _surviving_young_words to adjust for the correct cset index.

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Commit messages:
 - 8228609: G1 copy cost prediction uses used vs. actual copied bytes

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/927/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=927&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8228609
  Stats: 19 lines in 4 files changed: 12 ins; 1 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/927.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/927/head:pull/927

PR: https://git.openjdk.java.net/jdk11u-dev/pull/927