Sergius_Liu:

With multiple-workers, the loading process should be conducted before hand and will be ready when it is needed.


Multiple workers try to load the data in the background, while the model training is executed.
If the workers are not fast enough or bottlenecked by e.g. a local (spinning) HDD, they won’t be able to preload the next batch, which seems to be the case for your training routine.
Have a look at this post 44 for more information.