code: func validateSystemRequirements(mountUtil mount.Interface) (features, error) {
  	const (
  		cgroupMountType = "cgroup"
  		localErr        = "system validation failed"
  	)
  	var (
  		cpuMountPoint string
  		f             features
  	)
  	mountPoints, err := mountUtil.List()
  	if err != nil {
  		return f, fmt.Errorf("%s - %v", localErr, err)
  	}
  
  	expectedCgroups := sets.NewString("cpu", "cpuacct", "cpuset", "memory")
  	for _, mountPoint := range mountPoints {
  		if mountPoint.Type == cgroupMountType {
  			for _, opt := range mountPoint.Opts {
  				if expectedCgroups.Has(opt) {
  					expectedCgroups.Delete(opt)
  				}
  				if opt == "cpu" {
  					cpuMountPoint = mountPoint.Path
  				}
  			}
  		}
  	}
  
  	if expectedCgroups.Len() > 0 {
  		return f, fmt.Errorf("%s - Following Cgroup subsystem not mounted: %v", localErr, expectedCgroups.List())
  	}
  
  	// Check if cpu quota is available.
  	// CPU cgroup is required and so it expected to be mounted at this point.
  	periodExists, err := utilpath.Exists(utilpath.CheckFollowSymlink, path.Join(cpuMountPoint, "cpu.cfs_period_us"))
  	if err != nil {
  		klog.Errorf("failed to detect if CPU cgroup cpu.cfs_period_us is available - %v", err)
  	}
  	quotaExists, err := utilpath.Exists(utilpath.CheckFollowSymlink, path.Join(cpuMountPoint, "cpu.cfs_quota_us"))
  	if err != nil {
  		klog.Errorf("failed to detect if CPU cgroup cpu.cfs_quota_us is available - %v", err)
  	}
  	if quotaExists && periodExists {
  		f.cpuHardcapping = true
  	}
  	return f, nil
  }
docs: // checks if the required cgroups subsystems are mounted.
  // As of now, only 'cpu' and 'memory' are required.
  // cpu quota is a soft requirement.