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encoding/gob: use simple append-only buffer for encoding

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Bytes buffers have more API and are a little slower. Since appending
is a key part of the path in encode, using a faster implementation
speeds things up measurably.
The couple of positive swings are likely garbage-collection related
since memory allocation looks different in the benchmark now.
I am not concerned by them.

benchmark                            old ns/op     new ns/op     delta
BenchmarkEndToEndPipe                6620          6388          -3.50%
BenchmarkEndToEndByteBuffer          3548          3600          +1.47%
BenchmarkEndToEndSliceByteBuffer     336678        367980        +9.30%
BenchmarkEncodeComplex128Slice       78199         71297         -8.83%
BenchmarkEncodeFloat64Slice          37731         32258         -14.51%
BenchmarkEncodeInt32Slice            26780         22977         -14.20%
BenchmarkEncodeStringSlice           35882         26492         -26.17%
BenchmarkDecodeComplex128Slice       194819        185126        -4.98%
BenchmarkDecodeFloat64Slice          120538        120102        -0.36%
BenchmarkDecodeInt32Slice            106442        107275        +0.78%
BenchmarkDecodeStringSlice           272902        269866        -1.11%

LGTM=ruiu
R=golang-codereviews, ruiu
CC=golang-codereviews
https://golang.org/cl/160990043
This commit is contained in:
Rob Pike 2014-10-17 20:51:15 -07:00
parent 9965e40220
commit 65dde1ed4b
4 changed files with 59 additions and 35 deletions
Download patch file Download diff file Expand all files Collapse all files

12
src/encoding/gob/codec_test.go
View file

@ -53,7 +53,7 @@ func testError(t *testing.T) {
// Test basic encode/decode routines for unsigned integers
func TestUintCodec(t *testing.T) {
defer testError(t)
b := new(bytes.Buffer)
b := new(encBuffer)
encState := newEncoderState(b)
for _, tt := range encodeT {
b.Reset()
@ -62,10 +62,10 @@ func TestUintCodec(t *testing.T) {
t.Errorf("encodeUint: %#x encode: expected % x got % x", tt.x, tt.b, b.Bytes())
}
}
decState := newDecodeState(b)
for u := uint64(0); ; u = (u + 1) * 7 {
b.Reset()
encState.encodeUint(u)
decState := newDecodeState(bytes.NewBuffer(b.Bytes()))
v := decState.decodeUint()
if u != v {
t.Errorf("Encode/Decode: sent %#x received %#x", u, v)
@ -78,10 +78,10 @@ func TestUintCodec(t *testing.T) {
func verifyInt(i int64, t *testing.T) {
defer testError(t)
var b = new(bytes.Buffer)
var b = new(encBuffer)
encState := newEncoderState(b)
encState.encodeInt(i)
decState := newDecodeState(b)
decState := newDecodeState(bytes.NewBuffer(b.Bytes()))
decState.buf = make([]byte, 8)
j := decState.decodeInt()
if i != j {
@ -125,7 +125,7 @@ func newDecodeState(buf *bytes.Buffer) *decoderState {
return d
}
func newEncoderState(b *bytes.Buffer) *encoderState {
func newEncoderState(b *encBuffer) *encoderState {
b.Reset()
state := &encoderState{enc: nil, b: b}
state.fieldnum = -1
@ -135,7 +135,7 @@ func newEncoderState(b *bytes.Buffer) *encoderState {
// Test instruction execution for encoding.
// Do not run the machine yet; instead do individual instructions crafted by hand.
func TestScalarEncInstructions(t *testing.T) {
var b = new(bytes.Buffer)
var b = new(encBuffer)
// bool
{