Yes it works! Using DataParallel(model, device_ids=[0,1,2,3])
First I try
CUDA_VISIBLE_DEVICES=2,3,4,5
...
    model = model.cuda()
    model = torch.nn.DataParallel(model, device_ids=[0,1])

And we got:
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 384.111                Driver Version: 384.111                   |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  GeForce GTX 108...  Off  | 00000000:04:00.0 Off |                  N/A |
| 23%   24C    P8     8W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   1  GeForce GTX 108...  Off  | 00000000:05:00.0 Off |                  N/A |
| 23%   25C    P8     8W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   2  GeForce GTX 108...  Off  | 00000000:08:00.0 Off |                  N/A |
| 23%   27C    P2    54W / 250W |    595MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   3  GeForce GTX 108...  Off  | 00000000:09:00.0 Off |                  N/A |
| 23%   26C    P2    53W / 250W |    569MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   4  GeForce GTX 108...  Off  | 00000000:84:00.0 Off |                  N/A |
| 23%   26C    P8     8W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   5  GeForce GTX 108...  Off  | 00000000:85:00.0 Off |                  N/A |
| 23%   25C    P8     8W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   6  GeForce GTX 108...  Off  | 00000000:88:00.0 Off |                  N/A |
| 23%   27C    P8     8W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   7  GeForce GTX 108...  Off  | 00000000:89:00.0 Off |                  N/A |
| 23%   25C    P8     9W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID   Type   Process name                             Usage      |
|=============================================================================|
|    2     52106      C   python                                       585MiB |
|    3     52106      C   python                                       559MiB |
+-----------------------------------------------------------------------------+

Then tried:
CUDA_VISIBLE_DEVICES=2,3,4,5
...
    model = model.cuda()
    model = torch.nn.DataParallel(model, device_ids=[0,1,2,3])

+-----------------------------------------------------------------------------+
| NVIDIA-SMI 384.111                Driver Version: 384.111                   |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  GeForce GTX 108...  Off  | 00000000:04:00.0 Off |                  N/A |
| 23%   24C    P8     8W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   1  GeForce GTX 108...  Off  | 00000000:05:00.0 Off |                  N/A |
| 23%   25C    P8     9W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   2  GeForce GTX 108...  Off  | 00000000:08:00.0 Off |                  N/A |
| 23%   32C    P2    55W / 250W |    595MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   3  GeForce GTX 108...  Off  | 00000000:09:00.0 Off |                  N/A |
| 23%   30C    P2    54W / 250W |    569MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   4  GeForce GTX 108...  Off  | 00000000:84:00.0 Off |                  N/A |
| 23%   30C    P2    53W / 250W |    569MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   5  GeForce GTX 108...  Off  | 00000000:85:00.0 Off |                  N/A |
| 23%   29C    P2    53W / 250W |    569MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   6  GeForce GTX 108...  Off  | 00000000:88:00.0 Off |                  N/A |
| 23%   27C    P8     8W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
|   7  GeForce GTX 108...  Off  | 00000000:89:00.0 Off |                  N/A |
| 23%   25C    P8     8W / 250W |     10MiB / 11172MiB |      0%      Default |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID   Type   Process name                             Usage      |
|=============================================================================|
|    2     52926      C   python                                       585MiB |
|    3     52926      C   python                                       559MiB |
|    4     52926      C   python                                       559MiB |
|    5     52926      C   python                                       559MiB |
+-----------------------------------------------------------------------------+

Now you can see everything work well!
Thank you very much for your patiently help! Never think about this problem is triggered by DataParallel. It should use all GPU that visible to python. I don’t know why it failed when I don’t provide device_ids.
Sincerely thanks you @albanD and @aplassard .
PyTorch community is prosperous thanks to your quick and helpful help. (Never think a library forum is so activated before I join here