Linux Administration Cookbook

vmstat

vmstat is a great way to report on memory statistics; by default, its output looks like this:

$ vmstatprocs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st 2  0   1544  65260      0 367336    0    0    57    78   45   47  0  0 100  0  0

Where vmstat excels, though, is the fact its initial report (the preceding output) is the information since boot, and you can add a digit to the end of your command, to get a rolling summary:

$ vmstat 5procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st 2  0   1544  65140      0 367336    0    0    57    77   45   47  0  0 100  0  0 0  0   1544  65140      0 367336    0    0     0     0   49   48  0  0 100  0  0 0 0 1544 ...