Hi, I think your time_tot reflects the amount of time it needs to process an epoch. I don’t know how meters work but the last timing 'time_tot'=t5-t0 is measuring the amount of time you need to process an epoch as t0 is outside the for loop.
I find it’s difficult to measure the time it takes to load the data but it’s probably really low. Realize you are reading RAM. It may happen (just an hypotesis) that using workers slows dataloading as you are not preprocessing and starting them runs a big bunch of code.