4.7. Configuring Virtual NUMA

In the Administration Portal, you can configure virtual NUMA nodes on a virtual machine and pin them to physical NUMA nodes on one or more hosts. The host’s default policy is to schedule and run virtual machines on any available resources on the host. As a result, the resources backing a large virtual machine that cannot fit within a single host socket could be spread out across multiple NUMA nodes. Over time these resources may be moved around, leading to poor and unpredictable performance. Configure and pin virtual NUMA nodes to avoid this outcome and improve performance.

Configuring virtual NUMA requires a NUMA-enabled host. To confirm whether NUMA is enabled on a host, log in to the host and run numactl --hardware. The output of this command should show at least two NUMA nodes. You can also view the host’s NUMA topology in the Administration Portal by selecting the host from the Hosts tab and clicking NUMA Support. This button is only available when the selected host has at least two NUMA nodes.

Note

If you define NUMA Pinning, the default migration mode is Allow manual migration only by default.

Configuring Virtual NUMA

  1. Click Compute → Virtual Machines and select a virtual machine.
  2. Click Edit.
  3. Click Show Advanced Options.
  4. Click the Host tab.
  5. Select the Specific Host(s) radio button and select the host(s) from the list. The selected host(s) must have at least two NUMA nodes.
  6. Click NUMA Pinning.
  7. In the NUMA Topology window, click and drag virtual NUMA nodes from the box on the right to host NUMA nodes on the left as required, and click OK.
  8. Select Strict, Preferred, or Interleave from the Tune Mode drop-down list in each NUMA node. If the selected mode is Preferred, the NUMA Node Count must be set to 1.

  9. You can also set the NUMA pinning policy automatically by selecting Resize and Pin NUMA from the CPU Pinning Polcy drop-down list under the CPU Allocation settings in the Resource Allocation tab:

    • None - Runs without any CPU pinning.
    • Manual - Runs a manually specified virtual CPU on a specific physical CPU and a specific host. Available only when the virtual machine is pinned to a Host.
    • Resize and Pin NUMA - Resizes the virtual CPU and NUMA topology of the virtual machine according to the Host, and pins them to the Host resources.
    • Dedicated - Exclusively pins virtual CPUs to host physical CPUs. Available for cluster compatibility level 4.7 or later. If the virtual machine has NUMA enabled, all nodes must be unpinned.
    • Isolate Threads - Exclusively pins virtual CPUs to host physical CPUs. Each virtual CPU gets a physical core. Available for cluster compatibility level 4.7 or later. If the virtual machine has NUMA enabled, all nodes must be unpinned.
  10. Click OK.
Note

If you do not pin the virtual NUMA node to a host NUMA node, the system defaults to the NUMA node that contains the host device’s memory-mapped I/O (MMIO), provided that there are one or more host devices and all of those devices are from a single NUMA node.