To answer your question, there is a deepcopy, though shared memory will be used for Tensor data.

Is this documented somewhere? Couldn’t find it on [1] and [2], but observed this behavior by writing some simple script
[1] Multiprocessing best practices — PyTorch 1.9.0 documentation 7
[2] Multiprocessing package - torch.multiprocessing — PyTorch 1.9.0 documentation 6