Hi,
With this option to false, every time your code hits a line line for sample in dataloader:, it will create a brand new set of workers to do this loading and will kill them on exit.
Meaning that if you have multiple dataloaders, the workers will be killed when you are done with one instantly.
If you make them persist, these workers will stay around (with their state) waiting for another call into that dataloader.
Setting this to True will improve performances when you call into the dataloader multiple times in a row (as creating the workers is expensive). But it also means that the dataloader will have some persistent state even when it is not used (which can use some RAM depending on your dataset).