refactor dataloader

utils/datasets.py

@@ -52,7 +52,7 @@ def create_dataloader(path, imgsz, batch_size, stride, opt, hyp=None, augment=Fa
                                   pad=pad)
 
     batch_size = min(batch_size, len(dataset))
-    nw = min([os.cpu_count(), batch_size if batch_size > 1 else 0, 0])  # number of workers
+    nw = min([os.cpu_count(), batch_size if batch_size > 1 else 0, 8])  # number of workers
     dataloader = torch.utils.data.DataLoader(dataset,
                                              batch_size=batch_size,
                                              num_workers=nw,