Does not work: root@n1cc[staging]:/sys/fs# mount -t tmpfs tmpfs cgroup/ root@n1cc[staging]:/sys/fs# cd cgroup/ root@n1cc[staging]:/sys/fs/cgroup# l total 0 root@n1cc[staging]:/sys/fs/cgroup# mkdir cpuset root@n1cc[staging]:/sys/fs/cgroup# mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset mount: cpuset already mounted or /sys/fs/cgroup/cpuset busy root@n1cc[staging]:/sys/fs/cgroup# uname -a Linux n1cc 3.10-1-amd64 #1 SMP Debian 3.10.3-1 (2013-07-27) x86_64 GNU/Linux Of course cpuset is not already mounted. Works: root@n1cc[staging]:/sys/fs# mount -t tmpfs tmpfs cgroup/ root@n1cc[staging]:/sys/fs# cd cgroup/ root@n1cc[staging]:/sys/fs/cgroup# mkdir cpuset root@n1cc[staging]:/sys/fs/cgroup# mount -t cgroup -ocpuset cpuset /sys/fs/cgroup/cpuset root@n1cc[staging]:/sys/fs/cgroup# uname -a Linux n1cc 3.9-1-amd64 #1 SMP Debian 3.9.8-1 x86_64 GNU/Linux Mounting cgroups using default options works on both kernels.
Works with 3.10.11. I am not sure but it probably started to work after reboot. I was trying to mount cpuset after umounting all cgroups mounted with command: # mount -t cgroup cgroup /sys/fs/cgroup
I had the same problem with kernel 3.19.3. If you mount cgroup in /sys/fs/cgroup, it's over. You can unmount it but you'll never be able to mount the cgroup subdirs under a newly created tmpfs, you get 'already mounted or busy' /proc/mounts shows cgroups is not mounted anywhere, if I reboot, everything works.