Performance Latency Issues with Citrix NetScaler and e1000 Network Adapters on VKS

Products

• VMware vSphere Kubernetes Service

Issue/Introduction

• Users hosting applications on VKS (VMware vSphere Kubernetes Service) using a Citrix NetScaler Load Balancer may experience significant latency.
• This article provides steps to identify and resolve performance degradation caused by virtual network adapter configurations.
• Application latency significantly higher than expected (e.g., >30 seconds).
• Performance degradation occurs specifically when routing traffic through the Citrix NetScaler Load Balancer, while alternative load balancers (such as Avi) perform within expected baselines.

Environment

VMware NSX
VKS

Cause

The issue is caused by the Citrix virtual machine (VM) utilizing an "e1000" virtual network adapter. The e1000 adapter is a legacy emulation driver that often results in significant CPU overhead and throughput bottlenecks when handling high-traffic enterprise workloads compared to the "vmxnet3" adapter.

Resolution

To resolve performance latency, migrate the virtual machine network adapter from e1000 to vmxnet3.

1. Power down the affected Citrix NetScaler virtual machine.
2. Log in to the vSphere Client and edit the virtual machine settings.
3. Identify the Network Adapter currently configured as e1000.
4. Remove the existing e1000 network adapter from the hardware list.
5. Add a new network adapter and ensure the adapter type is set to vmxnet3.
• Note: Ensure the new adapter is assigned to the same port group/network as the original adapter to maintain connectivity.
6. Power on the virtual machine.
7. Verify that the operating system recognizes the new vmxnet3 adapter.
• Note: Ensure the appropriate VMware Tools or drivers are installed within the guest OS to support vmxnet3.

    8. Perform latency benchmarks to confirm the application performance has normalized.

Additional Information

For detailed instructions on managing virtual network adapters and VMware Tools, review the VMware vSphere Documentation.

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