Work needs to be done to the cgroups lib and containerd metrics interfaces to support cgroups v2 support. With much of the work in 5.3 kernels this should be reasonable to start supporting as a first class feature and can be a replacement for v1 for some users.

runc recently gained support for v2 as well as crun.

(below are edited by maintainers)

runc checklist

See opencontainers/runc#2315

containerd checklist

• base support cgroup2 #3799
• PID metrics support cgroup2 #3799
• CPU metrics
• Memory metrics
• OOM handler: cgroup2: implement containerd.events.TaskOOM event #4273
• IO metrics: Added IO metrics for cgroup v2 #3919

containerd/CRI checklist

• metrics: Cgroupv2: Added CPU, Memory metrics  cri#1376
• enable cgroup namespace by default: cgroup2: unshare cgroup namespace for containers cri#1371
• enable cgroup namespace for pod sandboxes as well as for containers? (To be determined)
• disable cgroup namespace for privileged pods (discussed in add KEP for cgroups v2 support kubernetes/enhancements#1370): cgroup2: do not unshare cgroup namespace for privileged cri#1415
• systemd cgroup driver for rootless (seems working without additional work: https://github.com/AkihiroSuda/critest-rootless-cgroup2)

CI

• CI (crun): cgroup2 CI #4279
• CI (runc): cgroup2 CI: add RUNC_FLAVOR=runc #4408
• CI for rootless mode with systemd (will be a follow-up PR)