CPU frequencies in AHV vs in VM | Nutanix Community
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CPU frequencies in AHV vs in VM

H

Hello,

We have recently set up a new Nutanix infrastructure consisting of two clusters, each with three AHV nodes.

The hardware comprises ThinkAgile HX650 V3 CN servers, equipped with Intel(R) Xeon(R) Silver 4416+ CPUs (2GHz, up to 3.9GHz).

The BIOS of the AHVs is configured to Performance Schedutil.

Our concern is that the VMs are operating at a CPU frequency of 2GHz. Monitoring shows that the CPU frequency never exceeds 2GHz, while the AHV CPUs average around 2.8GHz.

Is this behavior a bug, or is it by design? Is there a way to change and increase the CPU frequencies used by the VMs? We are still learning about the Nutanix infrastructure and would appreciate your assistance.

Thank you.

4 replies

D
Nutanix Employee
  • DHutNutanix Employee
  • Nutanix Employee
  • 2 replies
  • March 25, 2025

Hi HeadQuaker,

 

This seems to be a known issue with Lenovo as described in KB-10316. See https://portal.nutanix.com/page/documents/kbs/details?targetId=kA00e000000btAuCAI. 

Hope this helps, if not make sure to contact support, they will be glad to be of assistance.

Cheers,

David

H
  • HeadQuaker
  • Author
  • Voyager
  • 1 reply
  • March 26, 2025
DHut wrote:

Hi HeadQuaker,

 

This seems to be a known issue with Lenovo as described in KB-10316. See https://portal.nutanix.com/page/documents/kbs/details?targetId=kA00e000000btAuCAI. 

Hope this helps, if not make sure to contact support, they will be glad to be of assistance.

Cheers,

David

Hello , no, it’s not that issue. Our servers are set to performance Schedutil. The main quest is why VMs are at 2ghz while the CPU can run at 3.9Ghz. I know 2Ghz is the base frequency but I’ve monitored the CPU in a VM and it never goes above 2Ghz

D
Nutanix Employee
  • DHutNutanix Employee
  • Nutanix Employee
  • 2 replies
  • March 26, 2025

I would recommend opening a support case, the SRE’s will be happy to assist.

A
  • AaronG
  • Voyager
  • 1 reply
  • March 29, 2025

We are seeing this exact behavior on some Xeon Gold hardware while investigating poor performance of a single core application that is bottlenecking system performance downstream.  CPU can do 4+ GHZ, but on RHEL8 VMs, never reports back more than 2.0 ghz, and is STRUGGLING.  Equivalent VMWare, Azure, Proxmox, GCP VMs have not exhibited this issue, seems to be a Nutanix thing or environmental issue.  Is there not a guide on “if you want to enable the host to run at full core speed” or “if you want the VM to run with CPU at full core speed” or “ignore this, here’s how to really measure” ?

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