Memory controller not set at boot #systemd #cgroup_v2

[mimasci]

Hi All,
here one of my experiences I want to share with you: I was not able to start anymore - after a system update (zypper dup) - an LXC container due to the not mounted memory controller.
Then, googling a lot, I forced cgroup at v1 and mount the memory controller, that solved the problem for months.
Later, after another system update, I was not able to boot and I had to switch to cgroup v2.
Then, by reading about cgroup and systemd man pages, I figured it out: the memory controller in /sys/fs/cgroup/cgroup.subtree_control was missing.
By adding it (echo “+memory” > /sys/fs/cgroup/cgroup.subtree_control) and restarting libvirtd service I could start again my container.
I hope this may help someone else had the same, or similar, issue.
Still I do not understand a couple of things:
(1) why the memory controller is missing in tumbleweed as expected according to systemd man pages - note: the problem persist also with a fresh installation -;
(2) how to set the memory controller at boot time in the proper way.
Anyone could help me about this two items above?
Thanks,
mimasci

[arvidjaar]

@mimasci

why the memory controller is missing in tumbleweed

bor@tw:~> cat /sys/fs/cgroup/cgroup.subtree_control 
memory pids
bor@tw:~> 

I never explicitly configured anything related to cgroups.

[mimasci]

Thank you for your feedback @arvidjaar
Maybe one of the services/applications I am used to include in my tumbleweed setup implies the missing memory controller.
mimasci