I’m using cgroups v2 in my ubuntu24.04, and I’m confused about the root control group because some items are missing compared to the non-root control group, taking cpu controller for example:

$ ll /sys/fs/cgroup/
...
-rw-r--r--  1 root root 0 Nov 27 16:46 cpu.pressure
-r--r--r--  1 root root 0 Nov 27 16:46 cpu.stat
-r--r--r--  1 root root 0 Nov 27 16:46 cpu.stat.local
...

there are only three items for the cpu contoller but ten:

$ ll /sys/fs/cgroup/test/
...
-rw-r--r--  1 root root 0 Dec  2 20:41 cpu.idle
-rw-r--r--  1 root root 0 Dec  2 20:41 cpu.max
-rw-r--r--  1 root root 0 Dec  2 20:41 cpu.max.burst
-rw-r--r--  1 root root 0 Dec  2 20:41 cpu.pressure
-r--r--r--  1 root root 0 Dec  2 20:41 cpu.stat
-r--r--r--  1 root root 0 Dec  2 20:41 cpu.stat.local
-rw-r--r--  1 root root 0 Dec  2 20:41 cpu.uclamp.max
-rw-r--r--  1 root root 0 Dec  2 20:41 cpu.uclamp.min
-rw-r--r--  1 root root 0 Dec  2 20:41 cpu.weight
-rw-r--r--  1 root root 0 Dec  2 20:41 cpu.weight.nice
...

all controllers all enabled in the root control group:

$ cat /sys/fs/cgroup/cgroup.controllers 
cpuset cpu io memory hugetlb pids rdma misc

why are there only three items in the root control group for cpu controller? what makes the root control group so special?