Add controllerUID index to improve ReplicaSetController performance

Instead of listing all ReplicaSets in the namespace and checking their
controller UID, this patch adds a controllerUID index to the ReplicaSet
store and use it to get ReplicaSets with same controller, which reduces
the cost from O(#ReplicaSets) to O(1).

Benchmark results:
```
name                                 old time/op    new time/op    delta
GetReplicaSetsWithSameController-48    18.2µs ± 9%     0.4µs ± 5%  -97.64%  (p=0.008 n=5+5)

name                                 old alloc/op   new alloc/op   delta
GetReplicaSetsWithSameController-48    4.18kB ± 0%    0.05kB ± 0%  -98.85%  (p=0.008 n=5+5)

name                                 old allocs/op  new allocs/op  delta
GetReplicaSetsWithSameController-48      15.0 ± 0%       2.0 ± 0%  -86.67%  (p=0.008 n=5+5)
```

pkg/controller/replicaset/replica_set.go

@@ -69,6 +69,10 @@ const (
 
 	// The number of times we retry updating a ReplicaSet's status.
 	statusUpdateRetries = 1
+
+	// controllerUIDIndex is the name for the ReplicaSet store's index function,
+	// which is to index by ReplicaSet's controllerUID.
+	controllerUIDIndex = "controllerUID"
 )
 
 // ReplicaSetController is responsible for synchronizing ReplicaSet objects stored
@@ -96,6 +100,7 @@ type ReplicaSetController struct {
 	// rsListerSynced returns true if the pod store has been synced at least once.
 	// Added as a member to the struct to allow injection for testing.
 	rsListerSynced cache.InformerSynced
+	rsIndexer      cache.Indexer
 
 	// A store of pods, populated by the shared informer passed to NewReplicaSetController
 	podLister corelisters.PodLister
@@ -145,6 +150,20 @@ func NewBaseController(rsInformer appsinformers.ReplicaSetInformer, podInformer
 		UpdateFunc: rsc.updateRS,
 		DeleteFunc: rsc.deleteRS,
 	})
+	rsInformer.Informer().AddIndexers(cache.Indexers{
+		controllerUIDIndex: func(obj interface{}) ([]string, error) {
+			rs, ok := obj.(*apps.ReplicaSet)
+			if !ok {
+				return []string{}, nil
+			}
+			controllerRef := metav1.GetControllerOf(rs)
+			if controllerRef == nil {
+				return []string{}, nil
+			}
+			return []string{string(controllerRef.UID)}, nil
+		},
+	})
+	rsc.rsIndexer = rsInformer.Informer().GetIndexer()
 	rsc.rsLister = rsInformer.Lister()
 	rsc.rsListerSynced = rsInformer.Informer().HasSynced
 
@@ -201,17 +220,14 @@ func (rsc *ReplicaSetController) getReplicaSetsWithSameController(rs *apps.Repli
 		return nil
 	}
 
-	allRSs, err := rsc.rsLister.ReplicaSets(rs.Namespace).List(labels.Everything())
+	objects, err := rsc.rsIndexer.ByIndex(controllerUIDIndex, string(controllerRef.UID))
 	if err != nil {
 		utilruntime.HandleError(err)
 		return nil
 	}
-
-	var relatedRSs []*apps.ReplicaSet
-	for _, r := range allRSs {
-		if ref := metav1.GetControllerOf(r); ref != nil && ref.UID == controllerRef.UID {
-			relatedRSs = append(relatedRSs, r)
-		}
+	relatedRSs := make([]*apps.ReplicaSet, 0, len(objects))
+	for _, obj := range objects {
+		relatedRSs = append(relatedRSs, obj.(*apps.ReplicaSet))
 	}
 
 	if klog.V(2).Enabled() {

pkg/controller/replicaset/replica_set_test.go

@@ -36,6 +36,7 @@ import (
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/uuid"
 	"k8s.io/apimachinery/pkg/util/wait"
@@ -438,6 +439,36 @@ func TestGetReplicaSetsWithSameController(t *testing.T) {
 	}
 }
 
+func BenchmarkGetReplicaSetsWithSameController(b *testing.B) {
+	stopCh := make(chan struct{})
+	defer close(stopCh)
+	controller, informers := testNewReplicaSetControllerFromClient(clientset.NewForConfigOrDie(&restclient.Config{Host: "", ContentConfig: restclient.ContentConfig{GroupVersion: &schema.GroupVersion{Group: "", Version: "v1"}}}), stopCh, BurstReplicas)
+
+	targetRS := newReplicaSet(1, map[string]string{"foo": "bar"})
+	targetRS.Name = "rs1"
+	targetRS.ObjectMeta.OwnerReferences[0].UID = "123456"
+	informers.Apps().V1().ReplicaSets().Informer().GetIndexer().Add(targetRS)
+	relatedRS := newReplicaSet(1, map[string]string{"foo": "bar"})
+	relatedRS.Name = "rs2"
+	relatedRS.ObjectMeta.OwnerReferences[0].UID = "123456"
+	informers.Apps().V1().ReplicaSets().Informer().GetIndexer().Add(relatedRS)
+	for i := 0; i < 100; i++ {
+		unrelatedRS := newReplicaSet(1, map[string]string{"foo": fmt.Sprintf("baz-%d", i)})
+		unrelatedRS.Name = fmt.Sprintf("rs-%d", i)
+		unrelatedRS.ObjectMeta.OwnerReferences[0].UID = types.UID(fmt.Sprintf("%d", i))
+		informers.Apps().V1().ReplicaSets().Informer().GetIndexer().Add(unrelatedRS)
+	}
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		gotRSs := controller.getReplicaSetsWithSameController(targetRS)
+		if len(gotRSs) != 2 {
+			b.Errorf("Incorrect ReplicaSets number, expected 2, got: %d", len(gotRSs))
+		}
+	}
+}
+
 func TestPodControllerLookup(t *testing.T) {
 	stopCh := make(chan struct{})
 	defer close(stopCh)