Unfortunately, I got the message "lxc-cgroup: missing cgroup subsystem", that I've firstly intended as "I couldn't mount this cgroup at this session"
Briefly, asking about memory cgroup to LXC, everything was ok
while asking to linux not
Another confusing point to me, was the check of the dmesg output, that showed memory cgroup between the others
So, after a little of googling, I have understood like, the memory cgroup is just not enabled on Debian by default. That because having the cgroup.memory enabled, costs around 15Mb of ram, that is obviously a waste if you don't use that cgroup
In order to have the availability of said cgroup, you need to instruct the Grub by /etc/default/grub with the boot parameter cgroup_enable=memory
The amount of memory reserved to the cgroup nos is printed out during the boot time
In the end I could set my cgroup memory limit
The amount of memory reserved to the cgroup nos is printed out during the boot time