Bsd vmstat

Vmstat prints kernel info about processes, memory, disk, and cpu activity.
See also gnu vmstat.

procs  memory       page                    disks     faults         cpu
r b w  avm   fre   flt  re  pi  po    fr   sr ad0 ad1   in    sy    cs us sy id
0 0 0 550G  366M  1115  10   3   4 23328 15380   0   0 2754 189547 36863 20  6 74

Usage

vmstat 5  # refresh every 5s

columns

see the man page, it is quite good.