The Linux Storage and Filesystem Summit, day 1

I can't help thinking that the solution looks a lot like a PID controller. That is, page write speed is defined by the sum of three terms: one proportional to the amount of excess dirty pages, one proportional to the integral, and one proportional to the derivative.

The latter is the "feed-forward" term, and helps respond quickly to sudden changes. If the rate of page dirtying increases sharply, the rate of writeback should likewise take a sudden jump.