[libvirt-users] starting a domain only when you have enough resources

Hi all, I am running KVM on a 3.18 kernel. The system runs and Atom processor with 2Gb RAM. Using KVM you obviously can over allocate your resources: say you have 4 guests each configured with 1GB ram. Running all four at the same time, depending on the workload, can crash the system - I get a kernel trace when this happens. But let's consider a simpler case: one guest with 1.5 Gb RAM, ubuntu 14.03. During the installation the system will again crash. The memory statistics (top or proc/meminfo) will show that the FreeMemory goes down to 12Mb when this happens - which kind of makes sense considering the host will require some RAM to run. But the question is: does libvirt offer any way to prevent this from happening? Some way of not allowing the user to start a guest unless you have enough free memory. I know how much ram each guest has configured but that is not enough. I need to know how much the system has available, and just reading the free memory statistic does not help much since that is only a snapshot - when running a guest you can have 1gb free now, and 10 mb free 2 min later. Any ideas? Thanks, Andrei -- The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of or taking of any action in reliance upon this information by persons or entities other than the intended recipient is prohibited. If you receive this in error please contact the sender and delete the material from any computer immediately. It is the policy of Klas Limited to disavow the sending of offensive material and should you consider that the material contained in the message is offensive you should contact the sender immediately and also your I.T. Manager. Klas Telecom Inc., a Virginia Corporation with offices at 1101 30th St. NW, Washington, DC 20007. Klas Limited (Company Number 163303) trading as Klas Telecom, an Irish Limited Liability Company, with its registered office at Fourth Floor, One Kilmainham Square, Inchicore Road, Kilmainham, Dublin 8, Ireland.