Scale readahead with unchoked connections

client.go

@@ -287,7 +287,7 @@ func (cl *Client) readRaisePiecePriorities(t *torrent, off, _len int64) {
 		return
 	}
 	cl.raisePiecePriority(t, index, piecePriorityNext)
-	for i := 0; i < 5; i++ {
+	for i := 0; i < t.numConnsUnchoked()-2; i++ {
 		index++
 		if index >= t.NumPieces() {
 			break

torrent.go

@@ -77,6 +77,15 @@ type torrent struct {
 	GotMetainfo <-chan struct{}
 }
 
+func (t *torrent) numConnsUnchoked() (num int) {
+	for _, c := range t.Conns {
+		if !c.PeerChoked {
+			num++
+		}
+	}
+	return
+}
+
 func (t *torrent) addrActive(addr string) bool {
 	if _, ok := t.HalfOpen[addr]; ok {
 		return true