That’s strange, since the data loading time seem to be completely hidden behind the computation.
I just tried your code on my machine and simplified it a bit:

removed the test loop
used random inputs (torch.randn as data and torch.randint as target)
used an input batch of [20, 1, 100]


Using this I got a GPU utilization of 97% on a TITAN V GPU.
Does nvidia-smi show any utilization at all?
EDIT: Just saw your second post now.
Could you run nvidia-smi, as I’m not sure how the Windows task manager handles the GPU util and how accurate it is?