Oldie but goldie! Reminder that this feature still applies to latest Citrix ADC (formerly NetScaler ADC) versions.
Hypervisor, at least VMware and Citrix Hypervisors, might be reporting high CPU for the Citrix ADC or Gateway VPX instances.
If you check actual CPU on the Citrix ADC Dashboard, the CPU shows normal. But newly deployed VPX instance without real load on hypervisor shows high CPU and spikes to 90% and above on the hypervisor.
This is an expected behavior with latest Citrix ADC builds. With version NetScaler 11.1 and earlier VPX was sharing CPU with other VMs. From Citrix ADC 12.0 and later version, VPX will not share CPU by default.
In case you want to over-ride it, you can use CLI command to enable yield:
Display the current vpxparam settings:
show ns vpxparam
Allow each VM to use CPU resources that have been allocated to another VM but are not being used:
set ns vpxparam -cpuyield yes
YES: Allow allocated but unused CPU resources to be used by another VM.
NO: Reserve all CPU resources for the VM to which they have been allocated. This option shows higher percentage in hypervisor for VPX CPU usage.