swpd:

How to setup pyorch with cudnn8? By compiling from source with system cudnn8 library setup?


Yes, this would be the current option.



 swpd:

Gradients are still computed even with torch.no_grad() ?


No, but the backward pass through a “vanilla” convolution is a transposed convolution.
In the same manner, the forward pass of a transposed convolution can use the “backward kernel” of a vanilla convolution, which is why you are seeing the dgrad kernel here.