RFR: 8322732: ForkJoinPool may underutilize cores in async mode [v11]

[Doug Lea]

> This set of changes address causes of poor utilization with small numbers of cores due to overly aggressive contention avoidance. A number of further adjustments were needed to still avoid most contention effects in deployments with large numbers of cores

Doug Lea has updated the pull request incrementally with one additional commit since the last revision:

  re-enable rescan; slim down test

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19131/files
  - new: https://git.openjdk.org/jdk/pull/19131/files/4564b92c..1b818b48

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19131&range=10
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19131&range=09-10

  Stats: 21 lines in 2 files changed: 10 ins; 6 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/19131.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19131/head:pull/19131

PR: https://git.openjdk.org/jdk/pull/19131