[$] Custom out-of-memory killers in BPF

The out-of-memory (OOM) killer has long been a scary and controversial part
of the Linux kernel. It is summoned from some dark place when the system
as a whole (or, more recently, any given control group) is running so low
on memory that further allocations are not possible; its job is to kill off
processes until a sufficient amount of memory has been freed. Roman
Gushchin has found a way to make the OOM killer even scarier: adding the
ability to load
custom OOM killers in BPF.