What is atop?
The program atop is an interactive monitor to view the load on a Linux system. It shows the occupation of the most critical hardware resources (from a performance point of view) on system level, i.e. cpu, memory, disk and network.
KVM (Kernel-based Virtual Machine) is, on the other hand a full virtualization solution for Linux containing virtualization extensions (Intel VT or AMD-V). Using KVM, one can have Linux and Windows virtual machines running side by side on the same hardware. Each virtual machine has private virtualized hardware: own kernel, a network card, disk, graphics adapter, etc. Since it has its own virtualized hardware, the virtual server will act completely on its own.