> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xloud.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Live vCPU & RAM Scaling

> Increase or decrease vCPU and RAM on a running instance with no downtime using the Xloud Dashboard's Resource Adjustment dialog.

## Overview

Live vCPU and RAM scaling lets you adjust the compute resources of a **running instance
without rebooting**. Changes take effect immediately while the instance continues
serving traffic. The Dashboard provides a slider-based dialog for intuitive scaling
within the bounds configured on the instance's flavor.

<Info>**Xloud-Developed** — Bidirectional CPU hotplug (add AND remove vCPUs) and combined memory scaling (balloon + DIMM + virtio-mem) are developed by Xloud and ship with XAVS / XPCI.</Info>

<Note>
  **Prerequisites**

  * Instance must be in `Active` status
  * The instance must not be locked
  * The flavor must have hot-add enabled (`hw:cpu_min` or `hw:mem_min` extra specs) — if you do not see **Adjust Resources** in the actions menu, the flavor does not support live scaling
</Note>

***

## Scale vCPU or RAM

<Tabs>
  <Tab title="Dashboard" icon="gauge">
    <Steps titleSize="h3">
      <Step title="Open the Resource Adjustment dialog">
        Navigate to **Compute > Instances**. Click the **More** dropdown on
        the instance row, then select **Adjust Resources** under the
        **Configuration Update** group.

        <Note>
          This action only appears for instances in `Active` status whose flavor
          has hot-add enabled. If you do not see it, contact your administrator
          to configure a hot-add-enabled flavor.
        </Note>
      </Step>

      <Step title="Adjust resources with sliders">
        The dialog shows the current state and adjustment controls:

        | Field              | Description                                                                 |
        | ------------------ | --------------------------------------------------------------------------- |
        | **Instance**       | Instance name (read-only)                                                   |
        | **Current Info**   | Current vCPU count and memory allocation (read-only)                        |
        | **vCPUs**          | Slider input — drag or type to set between minimum and maximum vCPUs        |
        | **Memory (GiB)**   | Slider input — adjust between minimum and maximum memory in 0.25 GiB steps  |
        | **Make permanent** | Checkbox — persist the configuration after a soft reboot (default: checked) |

        The dialog fetches the live instance status to determine the current and
        allowed resource ranges. Color-coded hints indicate the scaling method:

        | Color  | Meaning                                             |
        | ------ | --------------------------------------------------- |
        | Green  | virtio-mem — fully adjustable in both directions    |
        | Yellow | No balloon driver detected — limited memory scaling |
        | Blue   | DIMM hotplug information                            |

        <Tip>
          The vCPU slider step aligns to the CPU thread count configured in the
          flavor. For example, with 2 threads per core, vCPUs adjust in steps of 2.
        </Tip>
      </Step>

      <Step title="Apply the change">
        Click **Confirm**. The change takes effect immediately — no reboot required.

        <Warning>
          Scaling **down** RAM while applications are using it may cause
          out-of-memory events inside the guest. Check application memory usage
          before reducing RAM.
        </Warning>
      </Step>

      <Step title="Verify inside the instance">
        SSH into the instance and confirm the new resources:

        ```bash title="Check vCPU count" theme={null}
        lscpu | grep "^CPU(s):"
        ```

        ```bash title="Check available RAM" theme={null}
        free -h
        ```

        <Check>The guest OS shows the updated vCPU count and memory — live scaling applied successfully with zero downtime.</Check>
      </Step>
    </Steps>
  </Tab>

  <Tab title="CLI" icon="terminal">
    ```bash title="Source credentials" theme={null}
    source openrc.sh
    ```

    Live resource adjustment uses the Xloud-developed Nova API extension. The
    `openstack` CLI does not have a native command for this operation.

    <CodeGroup>
      ```bash title="Check current live resource status" theme={null}
      curl -s -H "X-Auth-Token: $TOKEN" \
        "$NOVA_ENDPOINT/v2.1/servers/<INSTANCE_ID>/xloud-status" | python3 -m json.tool
      ```

      ```bash title="Adjust vCPU count" theme={null}
      curl -X POST -H "X-Auth-Token: $TOKEN" \
        -H "Content-Type: application/json" \
        -d '{"current_vcpus": 4}' \
        "$NOVA_ENDPOINT/v2.1/os-xloud-adjust/<INSTANCE_ID>"
      ```

      ```bash title="Adjust memory (in MB)" theme={null}
      curl -X POST -H "X-Auth-Token: $TOKEN" \
        -H "Content-Type: application/json" \
        -d '{"current_memory_mb": 8192}' \
        "$NOVA_ENDPOINT/v2.1/os-xloud-adjust/<INSTANCE_ID>"
      ```

      ```bash title="Adjust both simultaneously" theme={null}
      curl -X POST -H "X-Auth-Token: $TOKEN" \
        -H "Content-Type: application/json" \
        -d '{"current_vcpus": 4, "current_memory_mb": 8192}' \
        "$NOVA_ENDPOINT/v2.1/os-xloud-adjust/<INSTANCE_ID>"
      ```
    </CodeGroup>
  </Tab>
</Tabs>

***

## Comparison: Live Scaling vs. Flavor Resize

|                       | **Live vCPU/RAM Scaling**                      | **Flavor Resize**                    |
| --------------------- | ---------------------------------------------- | ------------------------------------ |
| **Downtime**          | None — instance stays running                  | Reboot required                      |
| **Scope**             | vCPU and RAM only                              | vCPU, RAM, and disk                  |
| **Direction**         | Up or down within flavor envelope              | Up or down (disk: up only)           |
| **Confirmation step** | No — instant                                   | Yes — must confirm or revert         |
| **Dashboard action**  | More > Configuration Update > Adjust Resources | More > Configuration Update > Resize |
| **Use case**          | Responding to live load changes                | Permanent tier change                |

***

## Troubleshooting

<AccordionGroup>
  <Accordion title="Adjust Resources not visible in the menu" defaultOpen>
    The instance's flavor does not have live scaling enabled. The flavor must have
    `hw:cpu_min` or `hw:mem_min` extra specs set. Contact your administrator to
    configure a hot-add-enabled flavor, or resize to a flavor that supports it.
  </Accordion>

  <Accordion title="Scaling request rejected">
    The requested value is outside the allowed range. The minimum and maximum are
    determined by the flavor's `hw:cpu_min` / `hw:mem_min` (minimum) and the flavor's
    vCPUs / RAM (maximum). Try a value within the slider range.
  </Accordion>

  <Accordion title="Guest OS does not show new vCPUs">
    On older Linux kernels (before 4.15), new CPUs may need to be brought online manually:

    ```bash title="Bring hotplugged CPUs online" theme={null}
    for cpu in /sys/devices/system/cpu/cpu*/online; do echo 1 > $cpu; done
    ```

    Modern kernels (4.15+) bring CPUs online automatically.
  </Accordion>

  <Accordion title="Memory change has no effect">
    The guest OS memory balloon driver may not be loaded. Check inside the guest:

    ```bash title="Check balloon driver" theme={null}
    lsmod | grep virtio_balloon
    ```

    If not loaded: `modprobe virtio_balloon` and add `virtio_balloon` to `/etc/modules`
    for persistence.
  </Accordion>
</AccordionGroup>

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Admin: Enable Live Scaling" href="/services/compute/live-resize-admin" color="#197560">
    Configure flavors with hot-add extra specs and resource bounds
  </Card>

  <Card title="Resize Instance" href="/services/compute/resize-instance" color="#197560">
    Standard flavor resize — change vCPU, RAM, and disk with a reboot
  </Card>

  <Card title="Flavors" href="/services/compute/flavors" color="#197560">
    View available flavors and their hot-add capabilities
  </Card>

  <Card title="Launch an Instance" href="/services/compute/launch-instance" color="#197560">
    Create an instance with a hot-add-enabled flavor
  </Card>
</CardGroup>