JDK-8352508 (and probably in earlier issues as well) showed an issue with reproduceability of optional collections: there is no good way to force optional collections, making us rely on random testing.

This is bad.

Improve the situation; one suggestion has been to introduce a flag that always makes all old gen regions in the collection set part of optional evacuation, exercising this functionality.

As an example this functionality could be used to create a test for JDK-8352508 that verifies optional collections in that scenario too.