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

The out-of-memory (OOM) killer has long been a scary and controversial partof the Linux kernel. It is summoned from some dark place when the systemas a whole (or, more recently, any given control group) is running so lowon memory that further allocations are not possible; its job is to kill offprocesses until a sufficient amount of memory has been freed. RomanGushchin has found a way to make the OOM killer even scarier: adding theability to loadcustom OOM killers in BPF.