Hi,
the GPU usage you mentioned above does not make sense to me.
If it means Utilization check by nvidia-smi, I think this thread can help you.
In my shallow view, there are many factors can effect GPU utilization when you load data by DataLoader, such as batch_size, pin_memory and num_workers. Generally, the more batch_size the more utilization will be and set pin_memory=True can also have an improvement, as for num_works you could have an experiment to fit your own dataset and hardware.
I can’t make sure these can help you, but it works for me.