Profiling for RNN Search model for multi-gpu.

[peterzhang2029]

pass_id	single-gpu	two-gpu	three-gpu	four-gpu
0	207.810512	193.126689	153.078007	131.083838
1	212.449378	191.684570	151.617278	129.824058
2	209.937869	190.296914	151.363250	129.944818
3	200.752512	196.673491	151.120727	130.697326
4	201.428616	193.513692	155.460599	131.675840
avg:	206.4757774	193.0590712	152.5279722	130.645176

GPU: TITAN X (Pascal)

paddlepaddle commit id: cb3bbbd

[shanyi15]

您好，此issue在近一个月内暂无更新，我们将于今天内关闭。若在关闭后您仍需跟进提问，可重新开启此问题，我们将在24小时内回复您。因关闭带来的不便我们深表歉意，请您谅解~感谢您对PaddlePaddle的支持!
Hello, this issue has not been updated in the past month. We will close it today for the sake of other user‘s experience. If you still need to follow up on this question after closing, please feel free to reopen it. In that case, we will get back to you within 24 hours. We apologize for the inconvenience caused by the closure and thank you so much for your support of PaddlePaddle Group!