Merge pull request #342 from bobrik/ivan/decoder-cache

Add decoder cache

decoder/decoder.go

@@ -23,6 +23,7 @@ type Decoder interface {
 type Set struct {
 	mu       sync.Mutex
 	decoders map[string]Decoder
+	cache    map[string][]string
 }
 
 // NewSet creates a Set with all known decoders
@@ -56,6 +57,7 @@ func NewSet() (*Set, error) {
 			"syscall":      &Syscall{},
 			"uint":         &UInt{},
 		},
+		cache: map[string][]string{},
 	}, nil
 }
 
@@ -87,6 +89,24 @@ func (s *Set) Decode(in []byte, label config.Label) ([]byte, error) {
 // DecodeLabels transforms eBPF map key bytes into a list of label values
 // according to configuration
 func (s *Set) DecodeLabels(in []byte, labels []config.Label) ([]string, error) {
+	// string(in) must not be a variable to avoid allocation:
+	// * https://github.com/golang/go/commit/f5f5a8b6209f8
+	if cached, ok := s.cache[string(in)]; ok {
+		return cached, nil
+	}
+
+	values, err := s.decodeLabels(in, labels)
+	if err != nil {
+		return nil, err
+	}
+
+	s.cache[string(in)] = values
+
+	return values, nil
+}
+
+// decodeLabels is the inner function of DecodeLabels without any caching
+func (s *Set) decodeLabels(in []byte, labels []config.Label) ([]string, error) {
 	values := make([]string, len(labels))
 
 	off := uint(0)

decoder/decoder_test.go

@@ -151,6 +151,77 @@ func TestDecodeLabels(t *testing.T) {
 	}
 }
 
+func BenchmarkCache(b *testing.B) {
+	in := []byte{
+		0x8, 0xab, 0xce, 0xef,
+		0xde, 0xad,
+		0xbe, 0xef,
+		0x8, 0xab, 0xce, 0xef, 0x8, 0xab, 0xce, 0xef,
+	}
+
+	labels := []config.Label{
+		{
+			Name: "number1",
+			Size: 4,
+			Decoders: []config.Decoder{
+				{
+					Name: "uint",
+				},
+			},
+		},
+		{
+			Name: "number2",
+			Size: 2,
+			Decoders: []config.Decoder{
+				{
+					Name: "uint",
+				},
+			},
+		},
+		{
+			Name: "number3",
+			Size: 2,
+			Decoders: []config.Decoder{
+				{
+					Name: "uint",
+				},
+			},
+		},
+		{
+			Name: "number4",
+			Size: 8,
+			Decoders: []config.Decoder{
+				{
+					Name: "uint",
+				},
+			},
+		},
+	}
+
+	s, err := NewSet()
+	if err != nil {
+		b.Fatal(err)
+	}
+
+	b.Run("direct", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_, err := s.decodeLabels(in, labels)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+
+	b.Run("cached", func(b *testing.B) {
+		for i := 0; i < b.N; i++ {
+			_, err := s.DecodeLabels(in, labels)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
 func zeroPaddedString(in string, size int) []byte {
 	if len(in) > size {
 		panic(fmt.Sprintf("string %q is longer than requested size %d", in, size))