This works for lxc 3 (and lxc 2, as long as you don't have
cruft in your config file, test it with:
   lxc-cgroup -o /dev/stdout -l INFO -n 104 cpuacct.usage
-- with 104 a valid lxc instance)

Tested on Debian buster and Debian jessie.

See the individual files for copyright and installation/configuration
information.

This is version 1.2 by schaefer@alphanet.ch