There are a few graphs you could use to monitoring your VM's CPU performance.
The first would be the VM CPU percent ready. VM CPU percent ready shows how often your VM is ready for CPU but was unable to get scheduled. This is often due to the load on the hypervisor. If there are many other VMs that are CPU dependent, it causes load on your hypervisor and you will see an increase in your VM's CPU percent ready. If your VM's CPU percent ready is above 10% it usually means the hypervisor is overloaded.
Another metric you could watch is CPU Utilization percentage. This shows how much CPU a VM is using from a hypervisor. This metric can be a little tricky. For example, if a VM is at 10% CPU Utilization it can seem low. However, if there are 25 VMs on that hypervisor, one VM using 10% is extremely high.
Finally a third metric you can watch is CPU percent stop. This metric shows how often the CPU cycles are stopped by the hypervisor due to VMs having to catch up on CPU cycles. If that is above ~5% it usually means the hypervisor is overloaded.
I do not have access to the vCenter console right now and off the top of my head I do not know if there are performance charts for 2 or 3. I am fairly sure that there is a performance chart for VM CPU percent ready, though. If you can find charts for all three, that is great. Otherwise there are other tools you can use to monitor the others. Either way, I hope this helps.
