We currently calculate a value that we call a read generation for pages that are candidates for eviction. We could calculate that value prior to adding a candidate to the queue, and use it to make a decision whether or not to add it at all.

The priority value is recalculated each time it's needed from a set of criteria. The criteria have become more complex, and it's really more of a priority value than a read generation now. It would also make sense to save the calculated generation in the eviction queue structure rather than recalculating it regularly.