RFR: 8360046: Scalability issue when submitting virtual threads with almost empty tasks [v16]

[Doug Lea]

> This set of updates reduces contention-based performance loss under heavy over-subscription, while also improving perfomance more generally.

Doug Lea has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 25 additional commits since the last revision:

 - Merge branch 'openjdk:master' into JDK-8360046
 - Seperate repolling policies
 - Faster quiescent termination
 - Fix push, refactor deactivate
 - Use absolute timed waits
 - Reduce deactivate/reactivate and cancelled timeout rates
 - Merge branch 'openjdk:master' into JDK-8360046
 - Reduce park/unpark rates
 - Add @Contended WorkQueue region. Adapt accordingly.
 - Revert Exchanger for separate PR
 - ... and 15 more: https://git.openjdk.org/jdk/compare/abecbe71...0f2f5908

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/26479/files
  - new: https://git.openjdk.org/jdk/pull/26479/files/48b8bda0..0f2f5908

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26479&range=15
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26479&range=14-15

  Stats: 279423 lines in 2896 files changed: 176769 ins; 61782 del; 40872 mod
  Patch: https://git.openjdk.org/jdk/pull/26479.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26479/head:pull/26479

PR: https://git.openjdk.org/jdk/pull/26479