diff --git a/pkg/api/testing/unstructured_test.go b/pkg/api/testing/unstructured_test.go
index 6d352b48bf..33d7d480b6 100644
--- a/pkg/api/testing/unstructured_test.go
+++ b/pkg/api/testing/unstructured_test.go
@@ -19,11 +19,13 @@ package testing
 import (
 	"math/rand"
 	"reflect"
+	"sort"
 	"testing"
 
-	"github.com/google/gofuzz"
+	fuzz "github.com/google/gofuzz"
+	jsoniter "github.com/json-iterator/go"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	"k8s.io/apimachinery/pkg/api/apitesting/fuzzer"
 	apiequality "k8s.io/apimachinery/pkg/api/equality"
 	"k8s.io/apimachinery/pkg/api/meta"
@@ -99,7 +101,7 @@ func doRoundTrip(t *testing.T, internalVersion schema.GroupVersion, externalVers
 		return
 	}
 
-	newUnstr, err := runtime.NewTestUnstructuredConverter(apiequality.Semantic).ToUnstructured(item)
+	newUnstr, err := runtime.DefaultUnstructuredConverter.ToUnstructured(item)
 	if err != nil {
 		t.Errorf("ToUnstructured failed: %v", err)
 		return
@@ -163,7 +165,7 @@ func TestRoundTripWithEmptyCreationTimestamp(t *testing.T) {
 			// attempt to re-convert unstructured object - conversion should not fail
 			// based on empty metadata fields, such as creationTimestamp
 			newObj := reflect.New(reflect.TypeOf(item).Elem()).Interface().(runtime.Object)
-			err = runtime.NewTestUnstructuredConverter(apiequality.Semantic).FromUnstructured(unstructObj.Object, newObj)
+			err = runtime.DefaultUnstructuredConverter.FromUnstructured(unstructObj.Object, newObj)
 			if err != nil {
 				t.Fatalf("FromUnstructured failed: %v", err)
 			}
@@ -171,44 +173,160 @@ func TestRoundTripWithEmptyCreationTimestamp(t *testing.T) {
 	}
 }
 
-func BenchmarkToFromUnstructured(b *testing.B) {
+func BenchmarkToUnstructured(b *testing.B) {
 	items := benchmarkItems(b)
 	size := len(items)
+	convertor := runtime.DefaultUnstructuredConverter
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		unstr, err := runtime.NewTestUnstructuredConverter(apiequality.Semantic).ToUnstructured(&items[i%size])
-		if err != nil {
-			b.Fatalf("unexpected error: %v", err)
-		}
-		obj := v1.Pod{}
-		if err := runtime.NewTestUnstructuredConverter(apiequality.Semantic).FromUnstructured(unstr, &obj); err != nil {
+		unstr, err := convertor.ToUnstructured(&items[i%size])
+		if err != nil || unstr == nil {
 			b.Fatalf("unexpected error: %v", err)
 		}
 	}
 	b.StopTimer()
 }
 
-func BenchmarkToFromUnstructuredViaJSON(b *testing.B) {
+func BenchmarkFromUnstructured(b *testing.B) {
 	items := benchmarkItems(b)
+	convertor := runtime.DefaultUnstructuredConverter
+	var unstr []map[string]interface{}
+	for i := range items {
+		item, err := convertor.ToUnstructured(&items[i])
+		if err != nil || item == nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+		unstr = append(unstr, item)
+	}
 	size := len(items)
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		data, err := json.Marshal(&items[i%size])
-		if err != nil {
-			b.Fatalf("unexpected error: %v", err)
-		}
-		unstr := map[string]interface{}{}
-		if err := json.Unmarshal(data, &unstr); err != nil {
-			b.Fatalf("unexpected error: %v", err)
-		}
-		data, err = json.Marshal(unstr)
-		if err != nil {
-			b.Fatalf("unexpected error: %v", err)
-		}
 		obj := v1.Pod{}
-		if err := json.Unmarshal(data, &obj); err != nil {
+		if err := convertor.FromUnstructured(unstr[i%size], &obj); err != nil {
 			b.Fatalf("unexpected error: %v", err)
 		}
 	}
 	b.StopTimer()
 }
+
+func BenchmarkToUnstructuredViaJSON(b *testing.B) {
+	items := benchmarkItems(b)
+	var data [][]byte
+	for i := range items {
+		item, err := json.Marshal(&items[i])
+		if err != nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+		data = append(data, item)
+	}
+	size := len(items)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		unstr := map[string]interface{}{}
+		if err := json.Unmarshal(data[i%size], &unstr); err != nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+	}
+	b.StopTimer()
+}
+
+func BenchmarkFromUnstructuredViaJSON(b *testing.B) {
+	items := benchmarkItems(b)
+	var unstr []map[string]interface{}
+	for i := range items {
+		data, err := json.Marshal(&items[i])
+		if err != nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+		item := map[string]interface{}{}
+		if err := json.Unmarshal(data, &item); err != nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+		unstr = append(unstr, item)
+	}
+	size := len(items)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		item, err := json.Marshal(unstr[i%size])
+		if err != nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+		obj := v1.Pod{}
+		if err := json.Unmarshal(item, &obj); err != nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+	}
+	b.StopTimer()
+}
+
+func BenchmarkToUnstructuredViaJSONIter(b *testing.B) {
+	items := benchmarkItems(b)
+	size := len(items)
+	var keys []string
+	for k := range jsonIterConfig {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	for _, name := range keys {
+		c := jsonIterConfig[name]
+		b.Run(name, func(b *testing.B) {
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				data, err := c.Marshal(&items[i%size])
+				if err != nil {
+					b.Fatalf("unexpected error: %v", err)
+				}
+				unstr := map[string]interface{}{}
+				if err := c.Unmarshal(data, &unstr); err != nil {
+					b.Fatalf("unexpected error: %v", err)
+				}
+			}
+			b.StopTimer()
+		})
+	}
+}
+
+var jsonIterConfig = map[string]jsoniter.API{
+	"default": jsoniter.ConfigDefault,
+	"fastest": jsoniter.ConfigFastest,
+	"compat":  jsoniter.ConfigCompatibleWithStandardLibrary,
+}
+
+func BenchmarkFromUnstructuredViaJSONIter(b *testing.B) {
+	items := benchmarkItems(b)
+	var unstr []map[string]interface{}
+	for i := range items {
+		data, err := jsoniter.Marshal(&items[i])
+		if err != nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+		item := map[string]interface{}{}
+		if err := json.Unmarshal(data, &item); err != nil {
+			b.Fatalf("unexpected error: %v", err)
+		}
+		unstr = append(unstr, item)
+	}
+	size := len(items)
+	var keys []string
+	for k := range jsonIterConfig {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	for _, name := range keys {
+		c := jsonIterConfig[name]
+		b.Run(name, func(b *testing.B) {
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				item, err := c.Marshal(unstr[i%size])
+				if err != nil {
+					b.Fatalf("unexpected error: %v", err)
+				}
+				obj := v1.Pod{}
+				if err := c.Unmarshal(item, &obj); err != nil {
+					b.Fatalf("unexpected error: %v", err)
+				}
+			}
+			b.StopTimer()
+		})
+	}
+}
diff --git a/staging/src/k8s.io/apimachinery/pkg/runtime/converter.go b/staging/src/k8s.io/apimachinery/pkg/runtime/converter.go
index dff56e0340..80343081f5 100644
--- a/staging/src/k8s.io/apimachinery/pkg/runtime/converter.go
+++ b/staging/src/k8s.io/apimachinery/pkg/runtime/converter.go
@@ -746,7 +746,7 @@ func isZero(v reflect.Value) bool {
 func structToUnstructured(sv, dv reflect.Value) error {
 	st, dt := sv.Type(), dv.Type()
 	if dt.Kind() == reflect.Interface && dv.NumMethod() == 0 {
-		dv.Set(reflect.MakeMap(mapStringInterfaceType))
+		dv.Set(reflect.MakeMapWithSize(mapStringInterfaceType, st.NumField()))
 		dv = dv.Elem()
 		dt = dv.Type()
 	}