An ESXi host does not use the C2 low-power state on AMD EPYC CPUs

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:
Even if C-states are enabled in the firmware setup of an ESXi host with an AMD EPYC CPU, you experience these symptoms:

• The vmkernel does not detect all the C-states correctly. 
• The power screen of the esxtop tool shows columns %C0 (percentage of time spent in C-state 0) and %C1 (percentage of time spent in C-state 1), but does not show column %C2.
• As a result, system performance per watt of power is not maximized.

Environment

VMware vSphere ESXi 6.5
VMware vSphere ESXi 6.7

Cause

This issue occurs due to a software incompatibility.

Resolution

This is a known issue affecting VMware ESXi 6.5.x and 6.7.x.

Currently, there is no resolution or workaround.