Comment 3 for bug 1271531

cgset -r cpu.cfs_quota_us=100000 -r cpu.cfs_period_us=1000 groupname
cgset -r cpu.cfs_period_us=100000 -r cpu.cfs_quota_us=1000 groupname

Both work for me, although the first probably should not. I have libcgroup 0.41-7, probably similar to libcgroup 0.41-6ubuntu1 in
Ubuntu 15.10 Wily Werewolf. Since this is the currently stable version, maybe you should check if it works there and close the bug as fixed.