RFR: 8359924: Deprecate and obsolete ParallelRefProcEnabled

Wed Jun 18 14:11:05 UTC 2025

Deprecating `ParallelRefProcEnabled`, which is used only by Parallel and G1, and both have it enabled by default via:

  if (FLAG_IS_DEFAULT(ParallelRefProcEnabled) && ParallelGCThreads > 1) {
    FLAG_SET_DEFAULT(ParallelRefProcEnabled, true);
  }

Disabling it offers little benefit and its presence incurs some implementation complexity in the reference-processor.

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

Commit messages:
 - deprecate-flag

Changes: https://git.openjdk.org/jdk/pull/25875/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25875&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8359924
  Stats: 19 lines in 3 files changed: 10 ins; 8 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25875.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25875/head:pull/25875

PR: https://git.openjdk.org/jdk/pull/25875