Linux / Unix Command: vmstat

vmstat - Report virtual memory statistics  

SYNOPSIS

vmstat [-n] [delay [ count]]
vmstat[-V]  

DESCRIPTION

vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity. The first report produced gives averages since the last reboot. Additional reports give information on a sampling period of length delay. The process and memory reports are instantaneous in either case.
 

Options

The -n switch causes the header to be displayed only once rather than periodically. delay is the delay between updates in seconds. If no delay is specified, only one report is printed with the average values since boot.
count is the number of updates. If no count is specified and delay is defined, count defaults to infinity.
The -V switch results in displaying version information.
 

FIELD DESCRIPTIONS

 

Procs

r: The number of processes waiting for run time.  
b: The number of processes in uninterruptable sleep.
w: The number of processes swapped out but otherwise runnable.  This 
   field is calculated, but Linux never desperation swaps.

 

Memory

swpd: the amount of virtual memory used (kB).
free: the amount of idle memory (kB).
buff: the amount of memory used as buffers (kB).

 

Swap

si: Amount of memory swapped in from disk (kB/s).
so: Amount of memory swapped to disk (kB/s).

 

IO

bi: Blocks sent to a block device (blocks/s).
bo: Blocks received from a block device (blocks/s).

 

System

in: The number of interrupts per second, including the clock.
cs: The number of context switches per second.

These are percentages of total CPU time.
us: user time
sy: system time
id: idle time 
 
 
Example
$ vmstat 1 5
 
Example for add timestamp
 
Create perl script 
$ vi timestamp.pl
#!/usr/bin/perl
while (<>) { print localtime() . ": $_"; }
 
$ vmstat 1 5 | ./timestamp.pl 
 
Example for monitor Memory and CPU
 
$/usr/bin/watch -n 5 '/usr/bin/vmstat -s -S M | /bin/grep -E "memory|cpu"' 
 
Thanks : www.thegeekstuff.com