RFR: 8294847: Fix calculation of G1 effective scanned cards prediction

[Thomas Schatzl]

Hi all,

  can I have reviews of this change that fixes the prediction of the actually to be scanned cards?

In particular, the current code completely misses the log buffer cards in the "effective" number of scanned cards. The change simply assumes that all pending log buffer cards are going to be scanned, ignoring duplicates.

Other changes are just removing related, unused or unnecessary code.

Depends on PR#10644, so please review that one first.

Testing: gha, local testing, tier1-5 with other changes in this patch series, perf testing with other changes in this patch series

Thanks,
  Thomas

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Depends on: https://git.openjdk.org/jdk/pull/10644

Commit messages:
 - initial version

Changes: https://git.openjdk.org/jdk/pull/10647/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10647&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294847
  Stats: 13 lines in 3 files changed: 4 ins; 7 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/10647.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10647/head:pull/10647

PR: https://git.openjdk.org/jdk/pull/10647