$ systemctl status machine.slice
● machine.slice - Virtual Machine and Container Slice
Loaded: loaded (/usr/lib/systemd/system/machine.slice; static; vendor preset: disabled)
Active: active since Wed 2018-06-13 08:45:07 BST; 1 day 15h ago
Docs: man:systemd.special(7)
Tasks: 0
Memory: 717.0M
CGroup: /machine.slice
$ cd /sys/fs/cgroup/memory/machine.slice
$ cat memory.usage_in_bytes
751915008
$ cat tasks
$ cat cgroup.procs
$
What does it mean, for the machine.slice
cgroup to be using 717MB, even though it is empty of processes/threads? Is it a kernel bug?
I can reproduce this simply by starting a VM with virt-manager, and then stopping it. If I repeat the cycle, the result is about the same - i.e. the system doesn't appear to be leaking these hundreds of megabytes.
Software version
$ uname -r
4.16.14-300.fc28.x86_64
$ rpm -q systemd libvirt-daemon
systemd-238-8.git0e0aa59.fc28.x86_64
libvirt-daemon-4.1.0-2.fc28.x86_64