introduce a buffer pool for large buffers (20k)

buffer_pool.go

@@ -56,13 +56,18 @@ func (b *packetBuffer) Len() protocol.ByteCount {
 }
 
 func (b *packetBuffer) putBack() {
-	if cap(b.Data) != int(protocol.MaxPacketBufferSize) {
-		panic("putPacketBuffer called with packet of wrong size!")
+	if cap(b.Data) == protocol.MaxPacketBufferSize {
+		bufferPool.Put(b)
+		return
 	}
-	bufferPool.Put(b)
+	if cap(b.Data) == protocol.MaxLargePacketBufferSize {
+		largeBufferPool.Put(b)
+		return
+	}
+	panic("putPacketBuffer called with packet of wrong size!")
 }
 
-var bufferPool sync.Pool
+var bufferPool, largeBufferPool sync.Pool
 
 func getPacketBuffer() *packetBuffer {
 	buf := bufferPool.Get().(*packetBuffer)
@@ -71,10 +76,18 @@ func getPacketBuffer() *packetBuffer {
 	return buf
 }
 
+func getLargePacketBuffer() *packetBuffer {
+	buf := largeBufferPool.Get().(*packetBuffer)
+	buf.refCount = 1
+	buf.Data = buf.Data[:0]
+	return buf
+}
+
 func init() {
-	bufferPool.New = func() interface{} {
-		return &packetBuffer{
-			Data: make([]byte, 0, protocol.MaxPacketBufferSize),
-		}
+	bufferPool.New = func() any {
+		return &packetBuffer{Data: make([]byte, 0, protocol.MaxPacketBufferSize)}
+	}
+	largeBufferPool.New = func() any {
+		return &packetBuffer{Data: make([]byte, 0, protocol.MaxLargePacketBufferSize)}
 	}
 }