View the number of visible CPU cores

This document describes how to view the number of visible CPU cores for a virtual machine (VM) instance.

When you view the details of a VM, you can verify if the VM has the default number of visible CPU cores, or if this number has been customized. Reducing the number of visible CPU cores for a VM can help reduce licensing costs without reducing Persistent Disk performance limits. However, reducing the number of visible CPU cores might affect network performance.

Before you begin

  • If you haven't already, then set up authentication. Authentication is the process by which your identity is verified for access to Google Cloud services and APIs. To run code or samples from a local development environment, you can authenticate to Compute Engine by selecting one of the following options:

    Select the tab for how you plan to use the samples on this page:

    Console

    When you use the Google Cloud console to access Google Cloud services and APIs, you don't need to set up authentication.

    gcloud

    1. Install the Google Cloud CLI, then initialize it by running the following command: 

      gcloud init
    2. Set a default region and zone.

    REST

    To use the REST API samples on this page in a local development environment, you use the credentials you provide to the gcloud CLI.

      Install the Google Cloud CLI, then initialize it by running the following command: 

      gcloud init

    For more information, see Authenticate for using REST in the Google Cloud authentication documentation.

Required roles

To get the permission that you need to view the details of a VM, ask your administrator to grant you the Compute Instance Admin (v1) (roles/compute.instanceAdmin.v1) IAM role on the VM or project. For more information about granting roles, see Manage access to projects, folders, and organizations.

This predefined role contains the compute.instances.get permission, which is required to view the details of a VM.

You might also be able to get this permission with custom roles or other predefined roles.

View the number of visible CPU cores for a VM

To determine if the number of visible CPU cores was customized for a VM, select one of the following options:

Console

  1. In the Google Cloud console, go to the VM instances page.

    Go to VM instances

  2. In the Name column, click the name of the VM.

    The details page of the VM opens and the Details tab is selected.

  3. In the Machine configuration section, check the value for Custom visible cores. If there is no value displayed, then the VM has the default number of visible CPU cores.

gcloud

To view the details of the VM, use the gcloud compute instances describe command.

gcloud compute instances describe VM_NAME \
    --zone=ZONE

Replace the following:

  • VM_NAME: the name of the VM.

  • ZONE: the zone where the VM is located.

If the number of visible CPU cores for the VM was customized, then the output contains the visibleCoreCount field as follows:

advancedMachineFeatures:
  visibleCoreCount: VISIBLE_CORE_COUNT
...

If the output doesn't contain the visibleCoreCount field, then the VM has the default number of visible CPU cores.

REST

To view the details of the VM, make a GET request to the instances.get method.

GET https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/VM_NAME

Replace the following:

  • PROJECT_ID: the ID of the project where the VM is located.

  • ZONE: the zone where the VM is located.

  • VM_NAME: the name of the VM.

If the number of visible CPU cores for the VM was customized, then the output contains the visibleCoreCount field as follows:

{
  ...
  "advancedMachineFeatures": {
    visibleCoreCount: VISIBLE_CORE_COUNT
  },
  ...
}

If the output doesn't contain the visibleCoreCount field, then the VM has the default number of visible CPU cores.

What's next