Skip to main content

Virtual Machine Metrics

The Gallium Console displays real-time performance metrics for each running virtual machine. These metrics are measured by the hypervisor and collected automatically — most require no software inside the guest.

Available Metrics​

The VM detail page displays the following charts:

  • CPU Utilization — percentage of allocated vCPU capacity in use.
  • Memory Utilization — percentage of the VM's memory in use as reported by the guest.
  • Network I/O — bytes transmitted and received per second, shown per network interface.
  • Disk I/O — bytes read and written per second, shown per virtual disk.
  • Disk IOPS — read and write operations per second, shown per virtual disk.

How Metrics Are Collected​

Every metric is measured by the hypervisor from outside the VM. However, the vantage point differs depending on the metric, and this determines whether anything needs to be installed inside the guest:

  • Host-observed metrics are measured by the hypervisor watching the VM process and its virtual devices. These work on every guest OS with no additional software. CPU, network, disk I/O, and disk IOPS are all host-observed.
  • Guest-reported metrics require cooperating software inside the VM to report values back to the hypervisor. Memory utilization is guest-reported.

In practice: CPU, network, and disk metrics always work. Memory is the one metric that depends on guest OS support.

Memory Metric Requirements​

Detailed memory statistics are reported through the VirtIO memory balloon device. The hypervisor attaches this device to every VM by default, but the guest must have the corresponding driver to report statistics back.

Linux​

The virtio_balloon kernel module is included in the mainline Linux kernel and loads automatically. Memory metrics work out of the box on Linux guests with no additional setup.

Windows​

Windows requires two components for memory metrics, and both must be present:

  1. VirtIO Balloon driver — the device driver that appears in Device Manager. This is included on the configuration drive and can be installed during setup via an Autounattend answer file or manually from the drivers\Balloon folder.

  2. Balloon statistics service (blnsvr.exe) — a Windows service from the VirtIO driver package that gathers memory statistics and feeds them to the balloon device. The driver alone does not report memory statistics.

A Windows VM can have the Balloon driver installed and appear healthy in Device Manager while still showing no memory data, simply because the statistics service is not running.

Troubleshooting​

Memory chart is blank but other metrics work​

This is the most common metrics issue. Because CPU, network, and disk metrics are host-observed, they continue to work even when memory reporting is not configured. A blank memory chart while other charts show data points to missing guest-side balloon support.

Windows VMs:

  1. Open Device Manager and confirm the VirtIO Balloon device is present and has no errors.
  2. Check that the BalloonService Windows service is installed and running.
  3. Contact support for available solutions.

Linux VMs:

  1. Confirm the balloon kernel module is loaded: 
    lsmod | grep virtio_balloon
  2. If it is not loaded, load it manually: 
    sudo modprobe virtio_balloon