Not a great one offhand, but here's a decent one from Apple, from back in the days when they put energy into documenting internal stuff like this. (As a result, some of the details in it are slightly out-of-date, but the general shape is still correct.)
This is very helpful (for someone who has never worked on Darwin)! The algorithm uses two FIFO lists with a "visited" bit (lazy promotion), and is a great idea! There are two differences between what is described and our algorithm, 1. the two FIFO lists are not fix-sized, which cannot guarantee quick demotion; 2. new data (hard fault) are inserted into the active list (I assume it is large than the inactive list), which is different from the quick demotion.
