[libvirt] [RFC] cgroup settings and systemd daemon-reload conflict

[Nikolay Shirokovskiy]

Hi, all.

It turns out that systemd daemon-reload reset settings that are managable
thru 'systemctl set-property' interface.

> virsh schedinfo tst3  | grep global_quota
global_quota   : -1
> virsh schedinfo tst3 --set global_quota=50000 | grep global_quota
global_quota   : 50000
> systemctl daemon-reload
> virsh schedinfo tst3  | grep global_quota
global_quota   : -1

This behaviour does not limited to cpu controller, same for blkio for example.
I checked different versions of systemd (219 - Feb 15, and quite recent 236 - Dec 17)
to make sure it is not kind of bug of old version. So systemd does not play well
with direct writes to cgroup parameters that managable thru systemd. Looks like
libvirtd needs to use systemd's dbus interface to change all such parameters.

I only wonder how this can be unnoticed for such long time (creating cgroup for domain
thru systemd - Jul 2013) as daemon-reload is called upon libvirtd package update. May
be I miss something?

Nikolay