private double memoryOverhead(double hostAdvertisedMemoryGb, NodeResources resources, boolean real) {
            double memoryShare = resources.memoryGiB() /
                                 ( hostAdvertisedMemoryGb - (real ? memoryOverhead : 0));
            return memoryOverhead * memoryShare;
        }
Returns the memory overhead resulting if the given advertised resources are placed on the given node

@param real true if the given resources are in real values, false if they are in advertised
node-repository/src/test/java/com/yahoo/vespa/hosted/provision/provisioning/VirtualNodeProvisioningCompleteHostCalculatorTest.java