Use msg copy method.

perf/thread_push_pull.lua

@@ -42,12 +42,13 @@ local child_code = [[
 	s:connect(connect_to)
 
 	local data = ("0"):rep(message_size)
-	local msg = zmq.zmq_msg_t.init_size(message_size)
+	local msg_data = zmq.zmq_msg_t.init_data(data)
+	local msg = zmq.zmq_msg_t.init()
 
 	local timer = zmq.stopwatch_start()
 
 	for i = 1, message_count do
-		msg:set_data(data)
+		msg:copy(msg_data)
 		assert(s:send_msg(msg))
 	end