[jdk21u-dev] RFR: 8343205: CompileBroker::possibly_add_compiler_threads excessively polls available memory

Mon Nov 4 18:13:44 UTC 2024

Almost clean backport of [JDK-8343205](https://bugs.openjdk.org/browse/JDK-8343205). I have included `get_c1_thread_count()` and `get_c2_thread_count()` from [JDK-8317562](https://bugs.openjdk.org/browse/JDK-8317562) (see 2nd commit).

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Commit messages:
 - Add getters from JDK-8317562.
 - Backport 75801992a7c626d409f66e2491082dba84c6fe45

Changes: https://git.openjdk.org/jdk21u-dev/pull/1123/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1123&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343205
  Stats: 29 lines in 2 files changed: 18 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1123.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1123/head:pull/1123

PR: https://git.openjdk.org/jdk21u-dev/pull/1123