RFR: 8321939: [GenShen] ShenandoahOldEvacRatioPercent=100 fails with divide-by-zero [v3]

[Y. Srinivas Ramakrishna]

On Fri, 15 Dec 2023 09:19:37 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> 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:**
>> - [x] GHA
>> - [x] code pipeline testing (TestPeriodicGC fails without the unrelated fix in https://github.com/openjdk/shenandoah/pull/372)
>> - [x] specjbb with SOEP=default,0,100 to verify that the issue is fixed
>
> Y. Srinivas Ramakrishna 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 ten additional commits since the last revision:
> 
>  - Merge branch 'should_unload_classes' into tenure_budget_8314599
>  - Merge branch 'master' into should_unload_classes
>  - JDK-8322150 should_unload_classes should return true only if a metaspace
>    oom has been signalled, and other conditions are met.
>  - Merge branch 'master' into tenure_budget_8314599
>  - Fix a scope issue with a local variable.
>  - jcheck trailing white-space.
>  - Merge branch 'master' into tenure_budget_8314599
>  - Fix another case where divide-by-zero could occur when
>    ShenandoahOldEvacRatioPercent is set to 100. Some slight refactoring in
>    the method.
>  - Fix divide-by-zero when ShenandoahOldEvacRatioPercent==100; minor
>    refactor & modification of documentation of flag

Converting to a draft until all failures are resolved satisfactorily.

This PR can be landed once the PR associated with JDK-8321816 integrates; the failures in GHA here have all been investigated and are either fixed by 8321816 or the result of changes from tip.

This PR is ready to commit in its current state.

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

PR Comment: https://git.openjdk.org/shenandoah/pull/369#issuecomment-1858110308
PR Comment: https://git.openjdk.org/shenandoah/pull/369#issuecomment-1870719247