Perf stack CPU


I am using perfstack for realtime performance reporting of my Network Infra. I have some queries regarding the same:

1. When plotting Peak CPU utilization of the switches, which were utilized around 50% many time in a month, peak CPU is showing not more then 20% monthly. which is not correct

2. Cant we have consolidated perfstack plotting (Utilization/errors/discards/buffer) for all interfaces on a specific switch/router.