reduce memory footprint

session.go

@@ -38,6 +38,7 @@ type Session struct {
 	dieLock   sync.Mutex
 	chAccepts chan *Stream
 
+	xmitPool  sync.Pool
 	dataReady int32 // flag data has arrived
 }
 
@@ -50,6 +51,10 @@ func newSession(config *Config, conn io.ReadWriteCloser, client bool) *Session {
 	s.chAccepts = make(chan *Stream, defaultAcceptBacklog)
 	s.bucket = int32(config.MaxReceiveBuffer)
 	s.bucketCond = sync.NewCond(&sync.Mutex{})
+	s.xmitPool.New = func() interface{} {
+		return make([]byte, (1<<16)+headerSize)
+	}
+
 	if client {
 		s.nextStreamID = 1
 	} else {
@@ -253,23 +258,16 @@ func (s *Session) keepalive() {
 // writeFrame writes the frame to the underlying connection
 // and returns the number of bytes written if successful
 func (s *Session) writeFrame(f Frame) (n int, err error) {
-	buf := make([]byte, headerSize+len(f.data))
+	buf := s.xmitPool.Get().([]byte)
 	buf[0] = f.ver
 	buf[1] = f.cmd
 	binary.LittleEndian.PutUint16(buf[2:], uint16(len(f.data)))
 	binary.LittleEndian.PutUint32(buf[4:], f.sid)
 	copy(buf[headerSize:], f.data)
 
 	s.writeLock.Lock()
-	n, err = s.conn.Write(buf)
-	s.writeLock.Unlock()
-	return n, err
-}
-
-// writeBinary writes the byte slice to the underlying connection
-func (s *Session) writeBinary(bts []byte) (n int, err error) {
-	s.writeLock.Lock()
-	n, err = s.conn.Write(bts)
+	n, err = s.conn.Write(buf[:headerSize+len(f.data)])
 	s.writeLock.Unlock()
+	s.xmitPool.Put(buf)
 	return n, err
 }

stream.go

@@ -2,7 +2,6 @@ package smux
 
 import (
 	"bytes"
-	"encoding/binary"
 	"sync"
 	"sync/atomic"
 
@@ -71,22 +70,10 @@ func (s *Stream) Write(b []byte) (n int, err error) {
 	}
 
 	frames := s.split(b, cmdPSH, s.id)
-	// preallocate buffer
-	buffer := make([]byte, len(frames)*headerSize+len(b))
-	bts := buffer
-
-	// combine frames into a large blob
 	for k := range frames {
-		bts[0] = version
-		bts[1] = frames[k].cmd
-		binary.LittleEndian.PutUint16(bts[2:], uint16(len(frames[k].data)))
-		binary.LittleEndian.PutUint32(bts[4:], frames[k].sid)
-		copy(bts[headerSize:], frames[k].data)
-		bts = bts[len(frames[k].data)+headerSize:]
-	}
-
-	if _, err = s.sess.writeBinary(buffer); err != nil {
-		return 0, err
+		if _, err := s.sess.writeFrame(frames[k]); err != nil {
+			return 0, err
+		}
 	}
 	return len(b), nil
 }