In Hub why would the CPU Utilization chart for an application show massive peaks for "CPU Entitlement"?

Products

• VMware Tanzu Platform - Hub

Issue/Introduction

When examining the CPU utilization chart for an app in Hub, a large parallel spike appears labeled "CPU entitlement" (see purple line in screenshot, below). 

What causes these seemingly very large spikes?

Resolution

This is the cpu_entitlement metric from https://docs.cloudfoundry.org/loggregator/container-metrics.html

If a Diego Cell is not already working at capacity, or if other workloads on the Diego Cell are idle, the Diego Cell can allocate more than the minimum amount of CPU time to an app instance.

The way diego calculates cpu entitlement allows the app to utilize CPU based on a ratio to memory of the app. If the diego cell has more capacity and the app spikes in CPU requirements, it can show up in high CPU entitlement spikes. The interaction between available capacity in the diego cell and the actions the app is performing can cause these types of spikes.