EVC enabled environment with HPE gen10 and HPE gen 11 overview

Products

• VMware vSphere ESXi

Issue/Introduction

• In a cluster where EVC mode is enabled consisting of the below.
  • AMD Zen 2 Generation with HPE gen10 with AMD EPYC 7702P 64-Core Processor 2 GHZ.
  • And HPE gen11 host with AMD EPYC 9354 32-Core Processor 3.25 GHZ. 
• VMs on the gen11 host get only 2 GHZ processors.

Environment

VMware vSphere ESXi 8.x

Resolution

• Does that mean EVC decides to expose Zen 2 regardless of whether the VM is first powered on on Zen 2 or Zen 4?
  
  • Yes, the configured EVC feature mask gets applied regardless.
• The behavior is expected.
• How to determine that using an EVC mode still allows applications to benefit from a CPU's faster clock speed.
  • Run a job which depends on CPU performance only. Dhrystone works for this.
  • And compare the results between the 2 hosts.

                  Or

• • Specifically to check for CPU frequency, enable CPU performance counters (vpmc.enable=TRUE), run an individual test from that suite while measuring cpu cycles consumed during individual run.
  • This should give a pretty accurate reading of the current CPU frequency.

Additional Information

• EVC featuremask can contain CPU family as shown below.
  • Here it is set to be Zen2.
    
    etc/vmware/config:
featMask.evc.cpuid.FAMILY = "Val:0x17"
featMask.evc.cpuid.MODEL = "Val:0x31"
featMask.evc.cpuid.STEPPING = "Val:0"
    
    
• Note that the 2GHz shown in the guest is not really what is being used.
• The VM will still consume the frequency provided by the underlying hardware.
• It is for consistency purpose that we report the lowest denominator of the CPU model.