DataLoader(datasets) become more and more slowly within iterations
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Hi ! Thanks for reporting.
Do you have the same slowdown when you iterate through the raw dataset object as well ? (no dataloader)
It would be nice to know whether it comes from the dataloader or not > Hi ! Thanks for reporting.
> Do you have the same slowdown when you iterate through the raw dataset object as well ? (no dataloader)
> It would be nice to know whether it comes from the dataloader or not

I did not iter data from raw dataset, maybe I will test later. Now I iter all files directly from `open(file)`,  around 20000it/s.
Hello, when I for loop my dataloader, the loading speed is becoming more and more slowly!
```
dataset = load_from_disk(dataset_path)  # around 21,000,000 lines

lineloader = tqdm(DataLoader(dataset, batch_size=1))
for idx, line in enumerate(lineloader):
     # do some thing for each line
```
In the begining, the loading speed is around 2000it/s, but after 1 minutes later, the speed is much slower, just around 800it/s.

And when I set `num_workers=4` in DataLoader, the loading speed is much lower, just 130it/s.

Could you please help me with this problem?
Thanks a lot!
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