Use msg:copy() instead of msg:set_data().

perf/remote_thr.lua

@@ -34,10 +34,11 @@ local s = ctx:socket(zmq.PUB)
 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()
 
 for i = 1, message_count do
-	msg:set_data(data)
+	msg:copy(msg_data)
 	assert(s:send_msg(msg))
 end
 

perf/thread_thr.lua

@@ -41,12 +41,13 @@ 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