Break reference cycle in load_state_dict (#20397)
Summary:
load_state_dict includes a recursive inner function `load` that captures
Tensors through the close-over variable `state_dict`. Because it's
recursive, it also captures itself leading to a reference cycle.
This breaks the reference cycle so that any Tensors in state_dict can be
collected immediately instead of waiting until the next GC cycle.
Alternatively, we could have passed `state_dict` and `metadata` as
arguments to load to prevent capture of Tensors. (That would still
result in cyclic garbage, but not any cyclic garbage of Tensors).
See:
https://github.com/pytorch/pytorch/issues/20199#issuecomment-491089004
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20397
Differential Revision: D15414834
Pulled By: colesbury
fbshipit-source-id: 4c2275a08b2d8043deb3779db28be03bda15872d
