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