Quick returns in predicates

plugin/pkg/scheduler/algorithm/predicates/predicates.go

@@ -204,6 +204,12 @@ func (c *MaxPDVolumeCountChecker) filterVolumes(volumes []api.Volume, namespace
 }
 
 func (c *MaxPDVolumeCountChecker) predicate(pod *api.Pod, nodeInfo *schedulercache.NodeInfo) (bool, error) {
+	// If a pod doesn't have any volume attached to it, the predicate will always be true.
+	// Thus we make a fast path for it, to avoid unnecessary computations in this case.
+	if len(pod.Spec.Volumes) == 0 {
+		return true, nil
+	}
+
 	newVolumes := make(map[string]bool)
 	if err := c.filterVolumes(pod.Spec.Volumes, pod.Namespace, newVolumes); err != nil {
 		return false, err
@@ -302,6 +308,12 @@ func NewVolumeZonePredicate(pvInfo PersistentVolumeInfo, pvcInfo PersistentVolum
 }
 
 func (c *VolumeZoneChecker) predicate(pod *api.Pod, nodeInfo *schedulercache.NodeInfo) (bool, error) {
+	// If a pod doesn't have any volume attached to it, the predicate will always be true.
+	// Thus we make a fast path for it, to avoid unnecessary computations in this case.
+	if len(pod.Spec.Volumes) == 0 {
+		return true, nil
+	}
+
 	node := nodeInfo.Node()
 	if node == nil {
 		return false, fmt.Errorf("node not found")

plugin/pkg/scheduler/generic_scheduler.go

@@ -135,7 +135,8 @@ func (g *genericScheduler) selectHost(priorityList schedulerapi.HostPriorityList
 // Filters the nodes to find the ones that fit based on the given predicate functions
 // Each node is passed through the predicate functions to determine if it is a fit
 func findNodesThatFit(pod *api.Pod, nodeNameToInfo map[string]*schedulercache.NodeInfo, predicateFuncs map[string]algorithm.FitPredicate, nodes api.NodeList, extenders []algorithm.SchedulerExtender) (api.NodeList, FailedPredicateMap, error) {
-	filtered := []api.Node{}
+	// Create filtered list with enough space to avoid growing it.
+	filtered := make([]api.Node, 0, len(nodes.Items))
 	failedPredicateMap := FailedPredicateMap{}
 
 	if len(predicateFuncs) == 0 {