Isn’t  pin_memory  supposed to speed up CUDA training since the tensors are loaded into page-locked memory on the host?

Yes it is, just couldn’t reproduce this in practice, yet :(. In my experience, I got up to 2x slower traininig. E.g., see https://github.com/rasbt/deep-learning-book/blob/master/code/model_zoo/pytorch_ipynb/convnet-resnet34-cifar10-pinmem.ipynb 1 Maybe I am doing something wrong (I also tried this as separate script.py files, and i tried a different machine and different models, always approx. the same behavior)