unable to hotplug cpulimit; cpu.* not in /sys?

[leesteken at pm.me]

Hi PVE-users,

Lately, on a no-subscription Proxmox (that I update regularly since release 6.0), I get the following error when changing the CPU limit of any (unpriviliged) container:

  Parameter verification failed. (400)
  cpulimit: unable to hotplug cpulimit: unable to open file '/sys/fs/cgroup/memory///lxc/115/ns/cpu.cfs_period_us'
   - No such file or directory

  /etc/pve/lxc/115.conf:
  arch: amd64
  console: 0
  cpulimit: 1.5
  hostname: vnc15
  memory: 2048
  #mp0: ...
  net0: name=eth0,bridge=vmbr0,firewall=1,gw=172.17.2.1,hwaddr=52:54:56:17:02:15,ip=172.17.2.15/24,type=veth
  onboot: 1
  ostype: debian
  protection: 1
  rootfs: qpool-zfs:subvol-115-disk-0,size=3G
  swap: 128
  unprivileged: 1

  [pve:pending]
  cpulimit: 1

Indeed, there are no cpu.* files in the directories of any of my containers. Is there something wrong with my setup?

Maybe someone has run into the same problem or can tell me how to fix this?

kind regards, Arjen