CPU Contention seen on a VM without performance issue

Products

• VCF Operations/Automation (formerly VMware Aria Suite)

Issue/Introduction

• 'CPU|Contention (%)' metric of the VM is continuously higher than expected (up to 40%).
• The same metric for the Host is then impacted.
• The same setup on a different Host hardware might not show the same behavior.
• Those other metrics don't show any issue: Co-stop, Overlap, Ready, Wait.
  In Aria Operations, they are represented by: Co-stop (%), Peak vCPU Overlap within collection cycle (%), Ready (%), Other Wait (%).
  In vCenter, they are represented by: Co-stop, Overlap, Ready, Wait.

Environment

Aria Operations 8.17 and previous versions.

Cause

In versions up to 8.17, the formula for the Contention was mapped to CPU Latency (%LAT_C in esxtop). This metric considers the effect of hyper-threading and CPU frequency, hence a difference depending on the Host hardware the VM is running on.

With this calculation, the Contention doesn't imply that there is an issue with the VM. Check the related performance metrics to verify if there is any performance issue: Co-stop, Overlap, Ready, Wait.

Resolution

This is resolved in Aria Operations 8.18.

Formula:
CPU|Contention (%) = (Co-Stop + Overlap + Ready + Wait) / (300000 * <#vCPUs>) * 100