Re: [PATCH 0/9] mm/damon: let users feed and tame/auto-tune DAMOS

[Andrew Morton]

On Thu, 30 Nov 2023 02:36:43 +0000 SeongJae Park <sj@xxxxxxxxxx> wrote:

> The core logic uses the below simple feedback loop algorithm to
> calculate the next aggressiveness level of the scheme from the current
> aggressiveness level and the current feedback (target_score and
> current_score).  It calculates the compensation for next aggressiveness
> as a proportion of current aggressiveness and distance to the target
> score.  As a result, it arrives at the near-goal state in a short time
> using big steps when it's far from the goal, but avoids making
> unnecessarily radical changes that could turn out to be a bad decision
> using small steps when its near to the goal.

fwiw, the above is a "proportional controller".  MGLRU has, in
vmscan.c, a PID controller (proportional, integral, derivative).  PID
controllers have better accuracy (the integral feedback) and better
stability (the derivative feedback).

Generalizing MGLRU's PID controller might be somewhat challenging!