# Datasets mapping slow down in the end

**URL:** <https://discuss.huggingface.co/t/datasets-mapping-slow-down-in-the-end/137519>\
**Category:** 🤗Datasets\
**Created:** [January 27, 2025, 10:13am UTC](https://discuss.huggingface.co/t/datasets-mapping-slow-down-in-the-end/137519 "2025-01-27T10:13:45Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![sleepywalker](https://avatars.discourse-cdn.com/v4/letter/s/6f9a4e/32.png) [@sleepywalker](https://discuss.huggingface.co/u/sleepywalker)\
**Post date:** [January 27, 2025, 10:13am UTC](https://discuss.huggingface.co/t/datasets-mapping-slow-down-in-the-end/137519/1 "2025-01-27T10:13:45Z")

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Hello! Can someone explain is it possible to fix dataset.map slowing down in the end with num\_of\_processes \> 1? For example, I got dataset with 60 millions samples and 98% of this dataset processed in 30 minutes and processes like 20k samples per second but from 98% to 99% it took 11 hours and processes few samples per second. I tried to reduce num\_of\_processes but it didn’t help. I’ve read other topics about it and answers from @lhoestq but I didn’t find any relevant answer