docs(python): clarify threading on two-CPU containers

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Gatefixer
2026-08-05 21:55:49 +00:00
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@@ -38,6 +38,25 @@ Stable releases are created about every 2 weeks. For the latest features and bug
pip install --pre --extra-index-url https://pypi.fury.io/lancedb/ lancedb
```
### Threading in CPU-limited containers
LanceDB uses separate pools for compute work and storage I/O. On a container with
two visible CPUs, current releases intentionally use one compute worker by default;
no manual configuration is needed. If every query logs an I/O core reservation
warning on a two-CPU container, upgrade from LanceDB 0.21.1 or earlier.
The two commonly tuned environment variables control different resources:
- `LANCE_CPU_THREADS` overrides the number of compute workers. One worker is the
appropriate setting for a two-CPU container when an explicit override is needed.
- `LANCE_IO_THREADS` controls concurrent storage operations, not reserved CPU
cores. Its default can be greater than the number of CPUs because I/O workers
spend much of their time waiting for storage.
Keep the defaults unless measurements show that the workload benefits from an
override. See the [Lance threading model](https://lance.org/guide/performance/#threading-model)
for the current defaults and tuning guidance.
## Usage
### Basic Example