Comment 2 for bug 1392176

systemd (in the sense of pid 1) doesn't do that. I. e. if you boot with init=/bin/systemd the only cgroup controller it puts tasks into (by default) is the "systemd" one, for that very reason. But if you boot with upstart (Ubuntu's default still), cgmanager creates cgroups. cgmanager puts tasks into *all* controllers (including "cpu"); as far as I know, this is so that user LXC containers work. So from cgmanager's POV this might be a design decision which can't otherwise be accomplished with the current kernel, but I'll let the cgmanager maintainers decide about whether this is a "wontfix" or whether there is a more elegant way to make user containers work.