del iterator on_run_end()

CHANGELOG.md

@@ -481,7 +481,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed bug where the training step output needed to be `deepcopy`-ed ([#9349](https://github.com/PyTorchLightning/pytorch-lightning/pull/9349))
 
 
-- Fixed freeing data iterators in loop `on_run_end` ([#9386](https://github.com/PyTorchLightning/pytorch-lightning/pull/9386))
+- Fixed freeing data iterators in loop `on_run_end` ([#9386](https://github.com/PyTorchLightning/pytorch-lightning/pull/9386)) ([#9915](https://github.com/PyTorchLightning/pytorch-lightning/pull/9915))
 
 
 - Fixed `BasePredictionWriter` not returning the batch_indices in a non-distributed setting ([#9432](https://github.com/PyTorchLightning/pytorch-lightning/pull/9432))

pytorch_lightning/loops/epoch/evaluation_epoch_loop.py

@@ -148,6 +148,7 @@ def on_run_end(self) -> EPOCH_OUTPUT:
         outputs = self.outputs
         # free memory
         self.outputs = []
+        del self._dataloader_iter
         self._dataloader_iter = None
         self._data_fetcher = None
         return outputs

pytorch_lightning/loops/epoch/training_epoch_loop.py

@@ -268,6 +268,7 @@ def on_run_end(self) -> None:
         if self._num_ready_batches_reached():
             self.update_lr_schedulers("epoch", update_plateau_schedulers=True)
 
+        del self._dataloader_iter
         self._dataloader_iter = None
 
         # if fault tolerant is enabled and process has been notified, exit.