Ygtjki

Does each directory under /sys/fs/cgroup/ represent a cgroup hierarchy, or a controller? (I assume it represents a cgroup hierarchy in the following, because multiple controllers can be mounted to the same cgroup hierarchy, while a controller can't be mounted to multiple cgroup hierarchies.)

1. 
   

   Do the directories and symlinks directly under /sys/fs/cgroup/
   represent controllers?

   
   
   

   Do the directories directly under /sys/fs/cgroup/ represent
   cgroup hierarchies?

   
   
   

   Are cpu,cpuacct, cpu, and cpuacct considered different
   controllers but the same cgroup hierarchy?

   
   
   

   Are net_cls,net_prio, net_cls, and net_prio considered
   different controllers but the same cgroup hierarchy?

   
   


2. 
   

   Must a cgroup be in exactly one cgroup hierarchy (i.e. one directory
   under /sys/fs/cgroup/, if I am correct), no more no less?

   
   
   

   All the directories under /sys/fs/cgroup/ have a subdirectory
   named docker. Is docker a cgroup, and does it belong to all
   those cgroup hierarchies represented by the directories under
   /sys/fs/cgroup/?

   
   

Thanks.

$ ls -l /sys/fs/cgroup/ 
total 0
dr-xr-xr-x 5 root root 0 Apr 5 17:52 blkio
lrwxrwxrwx 1 root root 11 Apr 5 17:52 cpu -> cpu,cpuacct
lrwxrwxrwx 1 root root 11 Apr 5 17:52 cpuacct -> cpu,cpuacct
dr-xr-xr-x 5 root root 0 Apr 5 17:52 cpu,cpuacct
dr-xr-xr-x 3 root root 0 Apr 5 17:52 cpuset
dr-xr-xr-x 5 root root 0 Apr 5 17:52 devices
dr-xr-xr-x 3 root root 0 Apr 5 17:52 freezer
dr-xr-xr-x 3 root root 0 Apr 5 17:52 hugetlb
dr-xr-xr-x 5 root root 0 Apr 5 17:52 memory
lrwxrwxrwx 1 root root 16 Apr 5 17:52 net_cls -> net_cls,net_prio
dr-xr-xr-x 3 root root 0 Apr 5 17:52 net_cls,net_prio
lrwxrwxrwx 1 root root 16 Apr 5 17:52 net_prio -> net_cls,net_prio
dr-xr-xr-x 3 root root 0 Apr 5 17:52 perf_event
dr-xr-xr-x 5 root root 0 Apr 5 17:52 pids
dr-xr-xr-x 2 root root 0 Apr 5 17:52 rdma
dr-xr-xr-x 6 root root 0 Apr 5 17:52 systemd
dr-xr-xr-x 5 root root 0 Apr 5 17:52 unified