# Troubleshoot performance

## CPU pinning

Diagnose and fix issues with CPU pinning for ScyllaDB Pods.

### Verify CPU pinning

Check QoS class:

```console
kubectl get pods -l 'app.kubernetes.io/name=scylla' \
  -o=jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.status.qosClass}{"\n"}{end}'
```

All ScyllaDB Pods should report `Guaranteed`.

Check ScyllaDB startup flags — when CPU pinning is active, ScyllaDB starts with `--overprovisioned=0`:

```console
kubectl logs <pod-name> -c scylla | grep -E 'overprovisioned|smp|cpuset'
```

Check that the `ContainerPerftune` Job ran for each ScyllaDB Pod:

```console
kubectl -n scylla-operator-node-tuning get jobs \
  -l scylla-operator.scylladb.com/node-config-job-type=ContainerPerftune
```

### Common issues

| Symptom                                | Cause                                                                 | Fix                                                                                         |
|----------------------------------------|-----------------------------------------------------------------------|---------------------------------------------------------------------------------------------|
| `qosClass: Burstable`                  | `agentResources` has no limits, or requests ≠ limits on any container | Set matching requests and limits on **both** `resources` and `agentResources`               |
| `--overprovisioned=1` in logs          | Pod is not Guaranteed QoS, or kubelet lacks static CPU policy         | Check QoS class and kubelet configuration                                                   |
| No `ContainerPerftune` job             | Pod is Burstable — tuning is skipped for non-Guaranteed Pods          | Fix QoS class                                                                               |
| `cpuset.cpus.effective` shows all CPUs | Kubelet not using static policy, or CPU request is fractional         | Enable `cpuManagerPolicy: static` and use integer CPU values                                |
| Latency spikes despite pinning         | IRQ affinity not set — perftune job failed or did not run             | Verify `NodeConfig` `disableOptimizations` is `false` (default) and check perftune job logs |

## See also

- [Configure CPU pinning](https://operator.docs.scylladb.com/v1.22/deploy-scylladb/before-you-deploy/configure-cpu-pinning.md) — how to set up CPU pinning.