# Long tail

The situation where most tasks finish quickly but one or two run much longer, so the whole run waits on them while workers sit idle.

Source: https://university.eugo.io/glossary/long-tail

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Usually caused by uneven partition sizes. The fix is splitting the oversized partitions, not adding workers.

## Related terms

- [Partition](https://university.eugo.io/glossary/partition) — One independently processable chunk of a dataset. Partition size is the main lever on how well a workload parallelizes.
- [Speedup](https://university.eugo.io/glossary/speedup) — How many times faster a distributed run is than the same work on one worker. Ideal speedup equals worker count; real speedup falls short of it.
- [Straggler](https://university.eugo.io/glossary/straggler) — A single task that runs far longer than its peers and holds up completion of the whole run.