[libvirt-users] Guests using more ram than specified

Hi, today I noticed that one of my HVs started swapping aggressively and noticed that the two guests running on it use quite a bit more ram than I assigned to them. They respectively were assigned 124G and 60G with the idea that the 192G system then has 8G for other purposes. In top I see the VMs using about 128G and 64G which means there is nothing left for the system. This is on a CentOS 7 system. Any ideas what causes this or how I can calculate the actual maximum amount of RAM I can assign to the guests on a HV without overcommitting RAM? Regards, Dennis