Expose virtual NUMA topology when CPU Hot-Plug is enabled on vSphere ESXi 8.0
Article ID: 313375
Updated On:
Products
VMware vSphere ESXi
Issue/Introduction
Symptoms:
Starting from ESXi 8.0 release, virtual machines that are compatible with “ESXi 8.0 or later” can be configured to expose virtual NUMA topology when CPU Hot-Plug is enabled.
By default, virtual machines with CPU Hot-Plug enabled will show a single virtual NUMA node. This behavior applies to virtual machines of compatibility before ESXi 8.0 and virtual machines of compatibility with ESXi 8.0 or later. For virtual machines of compatibility with ESXi 8.0 or later, any manual virtual NUMA related configuration will be ignored.
With the feature enabled, virtual machines can be supplied with manual configuration of virtual NUMA topology, or simply let ESXi automatically assign an accurate virtual NUMA topology even when CPU Hot-Plug is enabled. Hot-Plugged virtual CPUs and memory can potentially go into new virtual NUMA nodes.
Starting from ESXi 8.0 release, virtual machines that are compatible with “ESXi 8.0 or later” can be configured to expose virtual NUMA topology when CPU Hot-Plug is enabled.
By default, virtual machines with CPU Hot-Plug enabled will show a single virtual NUMA node. This behavior applies to virtual machines of compatibility before ESXi 8.0 and virtual machines of compatibility with ESXi 8.0 or later. For virtual machines of compatibility with ESXi 8.0 or later, any manual virtual NUMA related configuration will be ignored.
With the feature enabled, virtual machines can be supplied with manual configuration of virtual NUMA topology, or simply let ESXi automatically assign an accurate virtual NUMA topology even when CPU Hot-Plug is enabled. Hot-Plugged virtual CPUs and memory can potentially go into new virtual NUMA nodes.
Environment
VMware vSphere ESXi 8.0
Resolution
With the feature enabled, virtual machines can be supplied with manual configuration of virtual NUMA topology, or simply let ESXi automatically assign virtual NUMA topology even when CPU Hot-Plug is enabled. Hot-Plugged virtual CPUs and memory may go into new virtual NUMA nodes.
How to enable feature:
Configure virtual machines to enable CPU Hot-Plug, add numa.allowHotadd=TRUE to per virtual machine advanced configuration file.
To edit with vSphere Client:
How to enable feature:
Configure virtual machines to enable CPU Hot-Plug, add numa.allowHotadd=TRUE to per virtual machine advanced configuration file.
To edit with vSphere Client:
- Right-click on VM.
- Select Edit Settings.
- Click the Options tab.
- Highlight General under Advanced options and click Configuration Parameters.
- Add the parameter numa.allowHotadd and set the value TRUE.
- Windows Server 2012 R2
- Windows Server 2016
- Windows Server 2019
- Windows Server 2022
Additional Information
For more information about the Linux Kernel bug, see https://lore.kernel.org/linux-mm/[email protected]/#r
Impact/Risks:
When the feature is turned on, Hot-Plugging more virtual CPUs to the virtual machines could potentially create new virtual NUMA nodes. Exposing virtual NUMA topology when CPU Hot-Plug is enabled is dependent upon whether the guest OS supports CPU hot add into new NUMA nodes. Some versions of Linux could panic when Hot-Plugging "CPU only" virtual NUMA nodes because not all Linux kernels support CPU Hot-Plug features.. Please check with guest operating systems vendors to make sure the guest versions are compatible with this feature.
Impact/Risks:
When the feature is turned on, Hot-Plugging more virtual CPUs to the virtual machines could potentially create new virtual NUMA nodes. Exposing virtual NUMA topology when CPU Hot-Plug is enabled is dependent upon whether the guest OS supports CPU hot add into new NUMA nodes. Some versions of Linux could panic when Hot-Plugging "CPU only" virtual NUMA nodes because not all Linux kernels support CPU Hot-Plug features.. Please check with guest operating systems vendors to make sure the guest versions are compatible with this feature.
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