feat: optimize ListAll and ListAllByNamespace to return directly when nothing to select

Signed-off-by: likakuli <1154584512@qq.com>

Kubernetes-commit: 5a7e04b6cc70bd7624536e09b4e977e8f25cb476

tools/cache/listers.go

@@ -32,6 +32,10 @@ type AppendFunc func(interface{})
 
 // ListAll lists items in the store matching the given selector, calling appendFn on each one.
 func ListAll(store Store, selector labels.Selector, appendFn AppendFunc) error {
+	if labels.MatchesNothing(selector) {
+		return nil
+	}
+
 	selectAll := selector.Empty()
 	for _, m := range store.List() {
 		if selectAll {
@@ -55,6 +59,10 @@ func ListAll(store Store, selector labels.Selector, appendFn AppendFunc) error {
 // calling appendFn on each one.
 // If a blank namespace (NamespaceAll) is specified, this delegates to ListAll().
 func ListAllByNamespace(indexer Indexer, namespace string, selector labels.Selector, appendFn AppendFunc) error {
+	if labels.MatchesNothing(selector) {
+		return nil
+	}
+
 	if namespace == metav1.NamespaceAll {
 		return ListAll(indexer, selector, appendFn)
 	}

tools/cache/listers_test.go

@@ -138,3 +138,23 @@ func BenchmarkLister_Match_100k_100(b *testing.B) {
 func BenchmarkLister_Match_1M_100(b *testing.B) {
 	benchmarkLister(b, 1000000, 100, map[string]string{"match": "true"})
 }
+
+func benchmarkNothingLister(b *testing.B, numObjects int, numMatching int, labelSelector *metav1.LabelSelector) {
+	store := mustCreateStore(numObjects, numMatching, nil)
+	selector, err := metav1.LabelSelectorAsSelector(labelSelector)
+	if err != nil {
+		b.Fatalf("LabelSelectorAsSelector returned an error: %v", err)
+	}
+	b.ResetTimer()
+	for n := 0; n < b.N; n++ {
+		err := ListAll(store, selector, func(m interface{}) {
+		})
+		if err != nil {
+			b.Fatalf("ListAll returned an error: %v", err)
+		}
+	}
+}
+
+func BenchmarkLister_Match_1M_0(b *testing.B) {
+	benchmarkNothingLister(b, 1000000, 0, nil)
+}