Optimise the process of the CalculateSpreadPriority in selector_spreading.go

plugin/pkg/scheduler/algorithm/priorities/selector_spreading.go

@@ -62,6 +62,11 @@ func NewSelectorSpreadPriority(podLister algorithm.PodLister, serviceLister algo
 // pods which match the same service selectors or RC selectors as the pod being scheduled.
 // Where zone information is included on the nodes, it favors nodes in zones with fewer existing matching pods.
 func (s *SelectorSpread) CalculateSpreadPriority(pod *api.Pod, nodeNameToInfo map[string]*schedulercache.NodeInfo, nodeLister algorithm.NodeLister) (schedulerapi.HostPriorityList, error) {
+	nodes, err := nodeLister.List()
+	if err != nil {
+		return nil, err
+	}
+
 	selectors := make([]labels.Selector, 0, 3)
 	if services, err := s.serviceLister.GetPodServices(pod); err == nil {
 		for _, service := range services {
@@ -81,11 +86,6 @@ func (s *SelectorSpread) CalculateSpreadPriority(pod *api.Pod, nodeNameToInfo ma
 		}
 	}
 
-	nodes, err := nodeLister.List()
-	if err != nil {
-		return nil, err
-	}
-
 	// Count similar pods by node
 	countsByNodeName := make(map[string]float32, len(nodes))
 	countsByZone := make(map[string]float32, 10)