An administrator is investigating a complaint about poor performance and slow response times for a...

The performance issue is caused by Host CPU overcommitment, specifically regarding CPU scheduling (Ready Time) rather than total utilization.

While the Host CPU utilization is below 80% (meaning the processor has idle cycles), the configuration of 8 vCPUs per VM combined with a high 9:1 vCPU-to-pCPU ratio creates a bottleneck known as "Co-stop" or high "CPU Ready" time. The hypervisor scheduler must wait until 8 physical cores are available simultaneously to execute a single clock cycle for one VM. In a dense VDI environment, finding 8 free cores at the exact same moment is difficult, causing the VMs to pause (freeze) while waiting for the scheduler, even if the overall CPU usage of the host appears moderate. Reducing the vCPU count per VM would likely resolve the performance issues.