You may experience these performance issues with a multiple CPU virtual machine running on an ESX host:
- Poor transfer speeds when copying data to or from a virtual machine
- Backup jobs time out or are very slow
- A virtual machine performs poorly
To determine if multiple vCPUs assigned to your virtual machine is causing poor performance:
- Open a console prompt on the ESX host or initiate an SSH connection to it.
- Type esxtop and press Enter.
- On the CPU screen, check the %CSTP value. If this number is higher than 100, the performance issues may be caused by the vCPU count. Try lowering the vCPU count of the virtual machine by 1.
Note: The %CSTP value represents the amount of time a virtual machine with multiple virtual CPUs is waiting to be scheduled on multiple cores on the physical host. The higher the value, the longer it waits and the worse its performance. Lowering the number of vCPUs reduces the scheduling wait time.