Vmstat is often run with an interval of 1 second for a small number of seconds depending on kind of problem the administrator is trying to diagnose. Subsequent reports, until is reached, report data on the current state of the system every seconds. In this example, the first line of data provides the average since the last boot time. Often, the following form of the command is used: vmstat This data provides an average view of virtual memory and system usage since the last reboot. Use the vmstat command to run the program. It can be used to determine the root cause of performance and issues related to memory use.

Vmstat is a tool that collects and reports data about your system’s memory, swap, and processor resource utilization in real time. The documentation below which is from: Use vmstat to Monitor System Performance What is vmstat? To circumvent instruct vmstat to display in Megabytes: $ vmstat -S M The RAM is listed in bytes causing detail lines not to line up with column headings. One note is the software in its default parameters doesn't lend itself well to modern computers with abundant RAM. You can get a technical overview using man vmstat.

Linux monitor memory usage over time