RFR: 8321939: [GenShen] ShenandoahOldEvacRatioPercent=100 fails with divide-by-zero

Wed Dec 13 01:36:02 UTC 2023

The code that used the option ShenandoahOldEvacRatioPercent (SOEP) didn't correctly deal with the extremal setting of 100. Corrected the error and did some light refactoring in the vicinity, getting rid of some dead variables, adding documentation, and assertions. Also modified slightly the documentation of the option.

**Testing:**
- [ ] GHA
- [ ] code pipeline testing
- [ ] specjbb with SOEP=default,0,100 to verify that the issue is fixed

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Commit messages:
 - jcheck trailing white-space.
 - Merge branch 'master' into tenure_budget_8314599
 - Fix another case where divide-by-zero could occur when
 - Fix divide-by-zero when ShenandoahOldEvacRatioPercent==100; minor

Changes: https://git.openjdk.org/shenandoah/pull/369/files
 Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=369&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321939
  Stats: 172 lines in 3 files changed: 62 ins; 68 del; 42 mod
  Patch: https://git.openjdk.org/shenandoah/pull/369.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/369/head:pull/369

PR: https://git.openjdk.org/shenandoah/pull/369