Cgroups unified hierarchy has been on the horizon for a while, and is now reaching critical mass to begin switching over. Most all the controllers or equivalent are there, but there are mappings needed.

This issue should serve as the tracker for remaining issues to close this gap.

• ensure ebpf for devices maps to existing configs (device cgroup had a minor incompatibility (blacklisting isn't really possible))
• freezer controller (expected in linux 5.2)
• cgroupfs and/or systemd API
• There's no longer separate limits for kmem and kmem.tcp
• There's no longer a file to set "swappiness" for a single cgroup hierarchy
• There's no longer a way to disable OOMs through the memcg

Related #948