Properly allocating the cores to run the most VM’s efficiently is the goal of any virtualized system. That means your host server can only run as many virtual machines as it has cores (minus 1 for the host server), and usually a VM needs more than 1 core if it’s doing any real work. It’s recommended that your VM CPU allocation match up with a physical CPU core. When you create a new virtual machine, the VM requires at least 1 CPU core to operate. More often it’s the CPU causing resource shortages, especially if you operate a virtualized environment. These days, RAM and storage are cheap and plentiful. CPU load is one of the most important metrics for measuring hardware usage. Under utilization can show you opportunities to use hardware more efficiently. Gradual increases over time can help you predict hardware growth requirements. Unexpected spikes in resource usage can indicate a software or hardware problem. Monitoring, anticipating, and reacting to server load is a full time job in some organizations.

Linux view cpu usage