[$] Memory-management: tiered memory, huge pages, and EROFS

The kernel's memory-management developers have been busy in recent times;
it can be hard to keep up with all that has been happening in this core
area. In an attempt to catch up, here is a look at recent work
affecting tiered-memory systems, underutilized huge pages, and duplicated
file data in the Enhanced Read-Only Filesystem (EROFS).