double averageReal() {
            if (nodes.isEmpty()) { // we're estimating
                var initialResources = capacityPolicies.specifyFully(cluster.minResources().nodeResources(), clusterSpec);
                return nodeRepository.resourcesCalculator().requestToReal(initialResources,
                                                                          cloudAccount(),
                                                                          nodeRepository.exclusivity().allocation(clusterSpec),
                                                                          false).memoryGiB();
            }
            else {
                return nodes.stream()
                            .mapToDouble(node -> nodeRepository.resourcesCalculator().realResourcesOf(node, nodeRepository).memoryGiB())
                            .average()
                            .getAsDouble();
            }
        }
Returns the fraction of memory of the current allocation which is currently consumed by
fixed data structures which take the same amount of space regardless of document volume.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/autoscale/ClusterModel.java