[$] Teaching the OOM killer about control groups

The kernel's out-of-memory (OOM) killer is summoned when the system runsshort of free memory and is unable to proceed without killing one or moreprocesses. As might be expected, the policy decisions around whichprocesses should be targeted have engendered controversy for as long as theOOM killer has existed. The 4.19 development cycle is likely to includea new OOM-killer implementation that targets control groups rather thanindividual processes, but it turns out that there is significantdisagreement over how the OOM killer and control groups should interact.