About the Control Group File System

cgroup functionality is mounted as a hierarchical file system in /sys/fs/cgroup.

The directory /sys/fs/cgroup is also called the root control group. The contents of the root control group directory differ depending on which cgroup version is mounted on the system. For cgroups v2, the directory contents are as follows : 

ls /sys/fs/cgroup
cgroup.controllers      cpuset.mems.effective  memory.stat
cgroup.max.depth        cpu.stat               misc.capacity
cgroup.max.descendants  dev-hugepages.mount    sys-fs-fuse-connections.mount
cgroup.procs            dev-mqueue.mount       sys-kernel-config.mount
cgroup.stat             init.scope             sys-kernel-debug.mount
cgroup.subtree_control  io.pressure            sys-kernel-tracing.mount
cgroup.threads          io.stat                system.slice
cpu.pressure            memory.numa_stat       user.slice
cpuset.cpus.effective   memory.pressure
You can use the mkdir command to create cgroup subdirectories within the root control group. For example, you might create the following cgroup subdirectories:

  • /sys/fs/cgroup/MyGroups/

  • /sys/fs/cgroup/MyGroups/cgroup1

  • /sys/fs/cgroup/MyGroups/cgroup2

Note:

Best practice is to create child cgroups at least 2 levels deep inside the /sys/fs/cgroup. The examples in the preceding list follow this practice by using the first child group, MyGroups, as a parent that contains the different cgroups needed for the system.

Each cgroup in the hierarchy contains the following files:

cgroup.controllers

This read-only file lists the controllers available in the current cgroup. The contents of this file match the contents of the cgroup.subtree_control file in the parent cgroup.

cgroup.subtree_control

This file contains those controllers in the cgroup.controllers file that are enabled for the current cgroup's immediate child cgroups.

When a controller (for example, pids) is present in the cgroup.subtree_control file, the corresponding controller-interface files (for example, pids.max) are automatically created in the immediate children of the current cgroup.

For a sample procedure that creates child groups where you can implement resource management for an application, see Setting CPU Weight to Regulate Distribution of CPU Time.

To remove a cgroup, ensure that the cgroup doesn't contain other child groups, and then remove the directory. For example, to remove child group /sys/fs/cgroup/MyGroups/cgroup1 you can run the following command:. 

sudo rmdir /sys/fs/cgroup/MyGroups/cgroup1