NOTE: Reclaim does not work for the root cgroup, since we cannot set any
limits on the root cgroup.
+Note2: When panic_on_oom is set to "2", the whole system will panic.
+
2. Locking
The memory controller uses the following hierarchy
NOTE1: Enabling/disabling will fail if the cgroup already has other
cgroups created below it.
-NOTE2: This feature can be enabled/disabled per subtree.
+NOTE2: When panic_on_oom is set to "2", the whole system will panic in
+case of an oom event in any cgroup.
7. Soft limits