perf(pullsync): release reader buffer in handler (#1917)

pkg/pullsync/pullsync.go

@@ -260,7 +260,7 @@ func (s *Syncer) SyncInterval(ctx context.Context, peer swarm.Address, bin uint8
 
 // handler handles an incoming request to sync an interval
 func (s *Syncer) handler(ctx context.Context, p p2p.Peer, stream p2p.Stream) (err error) {
-	w, r := protobuf.NewWriterAndReader(stream)
+	r := protobuf.NewReader(stream)
 	defer func() {
 		if err != nil {
 			_ = stream.Reset()
@@ -311,6 +311,11 @@ func (s *Syncer) handler(ctx context.Context, p p2p.Peer, stream p2p.Stream) (er
 		return fmt.Errorf("make offer: %w", err)
 	}
 
+	// recreate the reader to allow the first one to be garbage collected
+	// before the makeOffer function call, to reduce the total memory allocated
+	// while makeOffer is executing (waiting for the new chunks)
+	w, r := protobuf.NewWriterAndReader(stream)
+
 	if err := w.WriteMsgWithContext(ctx, offer); err != nil {
 		return fmt.Errorf("write offer: %w", err)
 	}