CPU performance tools report significant CPU performace decrease after importing virtual machines to Cloud Director under a Flex org VDC

Products

• VMware Cloud Director

Issue/Introduction

• CPU performance tools report significant CPU performance decrease after importing virtual machines to Cloud Director under a Flex org VDC
• When comparing performance issues on virtual machines (VMs) in vCloud Director versus vCenter, there are no issues present on vCenter. The VM operated without any performance degradation, exhibiting stable CPU usage and minimal CPU ready/wait times. However, after importing the same VM into Cloud Director, we observed a noticeable degradation in CPU performance.
• Using the esxtop on ESXi, it seems we see %CSTP and %MLMTD values high during the perf test while VM is imported on Cloud Director

Environment

Cloud Director 

Cause

In FLEX allocation model, VM CPU Limit is based on the VM sizing policy of the virtual machine. The 'System Default' policy does not have unlimited CPU limit set by default and can cause performance tools to hit the limit and suggest a lower performance for the results. 

Resolution

The System Default policy is auto-generated for every VDC.

To fix, another custom policy with Unlimited limit can be created. The new policy can also be set as the default. The System Default policy in the VDC can be deleted as well if needed. 

For information, see Understanding VM Sizing, VM Placement, and vGPU Policies in VMware Cloud Director

Additional Information

 

• Understanding Allocation Models in VMware Cloud Director