This ticket covers the initial task of improvements in the card-marking algebra employed by Generational Shenandoah.

The extended algebra would use the card-table to track inter-regional, intra-genertional references in the old generation. The idea is to measure the impact of mixed collections on the duration of update-references and then determine if the proposed extension to the card-marking algebra would be helpful in addressing the current shortcoming of the update-refs phase for mixed evacuations (if measurably noticeably worse than in the case of young evacuations). The differences are expected to be noticeable, and benefits expected to accrue, in applications with largish long- to medium-lived footprint. The downside to watch for is the impact on young only collections unless the card-algebra and scanning are carefully designed and implemented.