cgroupv1

cgroupv1 has a hierarchy per-resource, for example:

ls /sys/fs/cgroup

returns:

blkio    cpu,cpuacct  freezer  net_cls           perf_event  systemd
cpu      cpuset       hugetlb  net_cls,net_prio  pids        unified
cpuacct  devices      memory   net_prio          rdma

Each resource hierarchy contains cgroups for this resource:

find /sys/fs/cgroup/pids -type d

returns:

/sys/fs/cgroup/pids
/sys/fs/cgroup/pids/docker
/sys/fs/cgroup/pids/user.slice
/sys/fs/cgroup/pids/system.slice
/sys/fs/cgroup/pids/system.slice/irqbalance.service
/sys/fs/cgroup/pids/system.slice/containerd.service
/sys/fs/cgroup/pids/system.slice/systemd-networkd.service
/sys/fs/cgroup/pids/system.slice/whoopsie.service
/sys/fs/cgroup/pids/system.slice/cron.service
/sys/fs/cgroup/pids/system.slice/avahi-daemon.service
/sys/fs/cgroup/pids/system.slice/systemd-logind.service
/sys/fs/cgroup/pids/machine.slice
...