2 files changed, 36 insertions, 2 deletions
diff --git a/src/encoding/binary/binary.go b/src/encoding/binary/binary.go
index 59a6c654d2..634995a5bd 100644
--- a/src/encoding/binary/binary.go
+++ b/src/encoding/binary/binary.go
@@ -480,8 +480,17 @@ var structSize sync.Map // map[reflect.Type]int
 func dataSize(v reflect.Value) int {
 	switch v.Kind() {
 	case reflect.Slice:
-		if s := sizeof(v.Type().Elem()); s >= 0 {
-			return s * v.Len()
+		t := v.Type().Elem()
+		if size, ok := structSize.Load(t); ok {
+			return size.(int) * v.Len()
+		}
+
+		size := sizeof(t)
+		if size >= 0 {
+			if t.Kind() == reflect.Struct {
+				structSize.Store(t, size)
+			}
+			return size * v.Len()
 		}
 
 	case reflect.Struct:
diff --git a/src/encoding/binary/binary_test.go b/src/encoding/binary/binary_test.go
index 4b22b28843..6cd0b92fa3 100644
--- a/src/encoding/binary/binary_test.go
+++ b/src/encoding/binary/binary_test.go
@@ -631,6 +631,31 @@ func BenchmarkWriteStruct(b *testing.B) {
 	}
 }
 
+func BenchmarkWriteSlice1000Structs(b *testing.B) {
+	slice := make([]Struct, 1000)
+	buf := new(bytes.Buffer)
+	var w io.Writer = buf
+	b.SetBytes(int64(Size(slice)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		Write(w, BigEndian, slice)
+	}
+	b.StopTimer()
+}
+
+func BenchmarkReadSlice1000Structs(b *testing.B) {
+	bsr := &byteSliceReader{}
+	slice := make([]Struct, 1000)
+	buf := make([]byte, Size(slice))
+	b.SetBytes(int64(len(buf)))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		bsr.remain = buf
+		Read(bsr, BigEndian, slice)
+	}
+}
+
 func BenchmarkReadInts(b *testing.B) {
 	var ls Struct
 	bsr := &byteSliceReader{}