real guest performance metrics such as memory and CPU

hello team, 

i need to know following metrics, 

current CPU usage 

current memory utilization. 

average cpu and memory utilization for 3 months. 

remember that i need to know real guest utilization details. 

i have report named all vm utilization report for virtual machines. . but the stats differ from what is showing inside guest OS. 

so what is the best of getting accurate Guest performance metrics

  • What do you consider real?  Polling the OS will get you what the OS thinks it uses, polling the host/vcenter will give you what resources the VM is actually consuming on the host after things like memory page dedupe and other virtualization technologies reduce the load.  "Real" means different things to different people.