vmstat

vmstat [options] [interval [count]]

System administration command. Print report on virtual memory statistics, including information on processes, memory, paging block I/O, traps, system and CPU usage. vmstat initially reports average values since the last system reboot. If given a sampling period interval in seconds, it prints additional statistics for each interval. If specified, vmstat exits when it has completed count reports. Otherwise, it continues until it receives a Ctrl-C, printing a new header line each time it fills the screen.