[$] Using DAMON for proactive reclaim

The DAMON patch set was first covered herein early 2020; this work, now in its34th revision, enables the efficient collection of information aboutmemory-usage patterns on Linux systems. That data can then be used toinfluence the kernel's memory-management subsystem; one possible way to dothat is to more aggressively reclaim memory that is not being used. Tothat end, DAMON author SeongJae Park is proposing aDAMON-based mechanism to perform user-controllable proactive reclaim.