RFR: 8372999: Parallel: Old generation min size constraint broken

Wed Dec 3 10:54:47 UTC 2025

Adding a missed min-gen-size-checking before shrinking old-gen.

`TEST=serviceability/tmtools/jstat/GcCapacityTest.java JTREG="JAVA_OPTIONS=-XX:+UseParallelGC -XX:InitialRAMPercentage=0"` fails before and passes after the fix.

Test: tier1

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

Commit messages:
 - pgc-shrink-below-min

Changes: https://git.openjdk.org/jdk/pull/28629/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28629&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372999
  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28629.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28629/head:pull/28629

PR: https://git.openjdk.org/jdk/pull/28629