I’ve been also experiencing the same issue for a while. I am not even sure I ever truly benefited using multiple-workers since I noticed this problem rather late. I have 8 cores and I have tried running with different number of workers 0, 1, 2, …, 8. The main thread (0 workers) gave me the fastest loading consistently. This is also the case for the data that is pre-loaded in the memory.
“pytorch version 1.8.1”