Misunderstanding documentation on enabling cgroup controllers

Hi folks, The documentation for enabling and disabling cgroup controllers at https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Docu... says that no controllers are enabled by default and to enable them, one needs to write into cgroup.subtree_control. I thought this meant that if I didn't enable a controller, I couldn't control those resources. However, I wrote a program to limit the number of processes in a cgroup and it works as expected - if I try to create more processes, I'm unable to. I didn't write "+pids" into cgroup.subtree_control - that file remains empty. Am I misunderstanding the documentation, then? Thanks.