Improve: pool buffer alloc

common/pool/alloc.go

@@ -0,0 +1,65 @@
+package pool
+
+// Inspired by https://github.com/xtaci/smux/blob/master/alloc.go
+
+import (
+	"errors"
+	"math/bits"
+	"sync"
+)
+
+var defaultAllocator *Allocator
+
+func init() {
+	defaultAllocator = NewAllocator()
+}
+
+// Allocator for incoming frames, optimized to prevent overwriting after zeroing
+type Allocator struct {
+	buffers []sync.Pool
+}
+
+// NewAllocator initiates a []byte allocator for frames less than 65536 bytes,
+// the waste(memory fragmentation) of space allocation is guaranteed to be
+// no more than 50%.
+func NewAllocator() *Allocator {
+	alloc := new(Allocator)
+	alloc.buffers = make([]sync.Pool, 17) // 1B -> 64K
+	for k := range alloc.buffers {
+		i := k
+		alloc.buffers[k].New = func() interface{} {
+			return make([]byte, 1<<uint32(i))
+		}
+	}
+	return alloc
+}
+
+// Get a []byte from pool with most appropriate cap
+func (alloc *Allocator) Get(size int) []byte {
+	if size <= 0 || size > 65536 {
+		return nil
+	}
+
+	bits := msb(size)
+	if size == 1<<bits {
+		return alloc.buffers[bits].Get().([]byte)[:size]
+	}
+
+	return alloc.buffers[bits+1].Get().([]byte)[:size]
+}
+
+// Put returns a []byte to pool for future use,
+// which the cap must be exactly 2^n
+func (alloc *Allocator) Put(buf []byte) error {
+	bits := msb(cap(buf))
+	if cap(buf) == 0 || cap(buf) > 65536 || cap(buf) != 1<<bits {
+		return errors.New("allocator Put() incorrect buffer size")
+	}
+	alloc.buffers[bits].Put(buf)
+	return nil
+}
+
+// msb return the pos of most significiant bit
+func msb(size int) uint16 {
+	return uint16(bits.Len32(uint32(size)) - 1)
+}

common/pool/alloc_test.go

@@ -0,0 +1,48 @@
+package pool
+
+import (
+	"math/rand"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAllocGet(t *testing.T) {
+	alloc := NewAllocator()
+	assert.Nil(t, alloc.Get(0))
+	assert.Equal(t, 1, len(alloc.Get(1)))
+	assert.Equal(t, 2, len(alloc.Get(2)))
+	assert.Equal(t, 3, len(alloc.Get(3)))
+	assert.Equal(t, 4, cap(alloc.Get(3)))
+	assert.Equal(t, 4, cap(alloc.Get(4)))
+	assert.Equal(t, 1023, len(alloc.Get(1023)))
+	assert.Equal(t, 1024, cap(alloc.Get(1023)))
+	assert.Equal(t, 1024, len(alloc.Get(1024)))
+	assert.Equal(t, 65536, len(alloc.Get(65536)))
+	assert.Nil(t, alloc.Get(65537))
+}
+
+func TestAllocPut(t *testing.T) {
+	alloc := NewAllocator()
+	assert.NotNil(t, alloc.Put(nil), "put nil misbehavior")
+	assert.NotNil(t, alloc.Put(make([]byte, 3, 3)), "put elem:3 []bytes misbehavior")
+	assert.Nil(t, alloc.Put(make([]byte, 4, 4)), "put elem:4 []bytes misbehavior")
+	assert.Nil(t, alloc.Put(make([]byte, 1023, 1024)), "put elem:1024 []bytes misbehavior")
+	assert.Nil(t, alloc.Put(make([]byte, 65536, 65536)), "put elem:65536 []bytes misbehavior")
+	assert.NotNil(t, alloc.Put(make([]byte, 65537, 65537)), "put elem:65537 []bytes misbehavior")
+}
+
+func TestAllocPutThenGet(t *testing.T) {
+	alloc := NewAllocator()
+	data := alloc.Get(4)
+	alloc.Put(data)
+	newData := alloc.Get(4)
+
+	assert.Equal(t, cap(data), cap(newData), "different cap while alloc.Get()")
+}
+
+func BenchmarkMSB(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		msb(rand.Int())
+	}
+}

common/pool/pool.go

@@ -1,15 +1,16 @@
 package pool
 
-import (
-	"sync"
-)
-
 const (
 	// io.Copy default buffer size is 32 KiB
 	// but the maximum packet size of vmess/shadowsocks is about 16 KiB
 	// so define a buffer of 20 KiB to reduce the memory of each TCP relay
-	bufferSize = 20 * 1024
+	RelayBufferSize = 20 * 1024
 )
 
-// BufPool provide buffer for relay
-var BufPool = sync.Pool{New: func() interface{} { return make([]byte, bufferSize) }}
+func Get(size int) []byte {
+	return defaultAllocator.Get(size)
+}
+
+func Put(buf []byte) error {
+	return defaultAllocator.Put(buf)
+}