make

container_id=`docker create -v /tmp/cgroupfs/meminfo:/proc/meminfo -m=15m ubuntu sleep 213133`

## In the second console tab
mkdir /tmp/cgroupfs
./cgroupfs /tmp/cgroupfs /docker/$container_id

## Go to the first tab
docker start $container_id

## Take a look at /tmp/cgroupfs/meminfo now
## cgroupfs file system should be able to show the memory usage of the container
root@linux-dev:/home/vagrant# cat /tmp/cgroupfs/meminfo
MemTotal:       15360 kB
MemFree:        13432 kB
MemAvailable:   13432 kB
Buffers:        0 kB
Cached:         1804 kB
SwapCached:     0 kB

## Enter docker container, you should see free is showing the real usage
docker exec -it $container_id bash
root@251d4d18bca6:/# free -m
             total       used       free     shared    buffers     cached
Mem:            15          2         12          0          0          1
-/+ buffers/cache:          0         14
Swap:            0          0          0

On debian/ubuntu
sudo apt-get install fuse