The output of nvidia-smi of mine:
Wed Aug 23 19:34:42 2017       
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 375.66                 Driver Version: 375.66                    |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  TITAN X (Pascal)    Off  | 0000:08:00.0     Off |                  N/A |
| 36%   60C    P2    96W / 250W |   6795MiB / 12189MiB |     61%      Default |
+-------------------------------+----------------------+----------------------+
|   1  TITAN X (Pascal)    Off  | 0000:09:00.0     Off |                  N/A |
| 30%   52C    P2    56W / 250W |  10363MiB / 12189MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   2  TITAN X (Pascal)    Off  | 0000:88:00.0     Off |                  N/A |
| 35%   59C    P2   105W / 250W |   6845MiB / 12189MiB |     96%      Default |
+-------------------------------+----------------------+----------------------+
|   3  TITAN X (Pascal)    Off  | 0000:89:00.0     Off |                  N/A |
| 40%   66C    P2   127W / 250W |   5027MiB / 12189MiB |     96%      Default |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID  Type  Process name                               Usage      |
|=============================================================================|
|    0     73255    C   ./build/tools/caffe                           6793MiB |
|    1      8248    C   ./build/tools/caffe                           4381MiB |
|    1      8464    C   ./build/tools/caffe                           2469MiB |
|    1     67991    C   python                                        3511MiB |
|    2     23050    C   ./build/tools/caffe                           6843MiB |
|    3     23050    C   ./build/tools/caffe                           5025MiB |
+-----------------------------------------------------------------------------+

But the confusing part is that the python script implements a3c using CPU, none of business with GPU(from my perspective).