what is Vmstate????

 vmstat is Linux command its basic work is display virtual memory statistics.

Its use for Linux Performance Monitoring.

vmstat by default will display the memory usage (including swap) as shown below.

$ vmstat
 
 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  0 305416 260688  29160 2356920    2    2     4     1    0    0  6  1 92  2  0
vmstat output contains the following fields:
  • Procs – r: Total number of processes waiting to run
  • Procs – b: Total number of busy processes
  • Memory – swpd: Used virtual memory
  • Memory – free: Free virtual memory
  • Memory – buff: Memory used as buffers
  • Memory – cache: Memory used as cache.
  • Swap – si: Memory swapped from disk (for every second)
  • Swap – so: Memory swapped to disk (for every second)
  • IO – bi: Blocks in. i.e blocks received from device (for every second)
  • IO – bo: Blocks out. i.e blocks sent to the device (for every second)
  • System – in: Interrupts per second
  • System – cs: Context switches
  • CPU – us, sy, id, wa, st: CPU user time, system time, idle time, wait time

1. vmstat – Display active and inactive memory

By default vmstat doesn’t display this information. Use option -a, to display active and inactive memory information as shown below.
 
$ vmstat -a
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free  inact active   si   so    bi    bo   in   cs us sy id wa st
 0  0 305416 253820 1052680 2688928    2    2     4     1    0    0  6  1 92  2  0

2. vmstat – Display number of forks since last boot

This displays all the fork system calls made by the system since the last boot. This displays all fork, vfork, and clone system call counts.
$ vmstat -f
     81651975 forks

3. vmstat – Execute Every x seconds (for y number of times)

To execute every 2 seconds, do the following. You have to press Ctrl-C to stop this.
$ vmstat 2
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 1  0      0 537144 182736 6789320    0    0     0     0    1    1  0  0 100  0  0 
 0  0      0 537004 182736 6789320    0    0     0     0   50   32  0  0 100  0  0 
..
To execute every 2 seconds for 10 times, do the following. You don’t need to press Ctrl-C in this case. After executing 10 times, it will stop automatically.
$ vmstat 2 10
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 1  0      0 537144 182736 6789320    0    0     0     0    1    1  0  0 100  0  0 
 0  0      0 537004 182736 6789320    0    0     0     0   50   32  0  0 100  0  0 
..

4. vmstat – Display timestamp

When you use vmstat to monitor the memory usage repeately, it would be nice to see the timestap along with every line item. Use option -t to display the time stamp as shown below.
$ vmstat -t 1 100
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ ---timestamp---
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  0      0 3608728 148368 3898200    0    0     0     0    1    1  0  0 100  0  0     2011-07-09 21:16:28 PDT
 0  0      0 3608728 148368 3898200    0    0     0     0   60   15  0  0 100  0  0     2011-07-09 21:16:29 PDT
 0  0      0 3608712 148368 3898200    0    0     0     0   32   28  0  0 100  0  0     2011-07-09 21:16:30 PDT
For me, the timestamp option worked in the following version.
$ vmstat -V
procps version 3.2.8
Note: If you use a older version of vmstat, option -t might not be available. In that case, use the method we suggested earlier to display timestamp in vmstat output.

5. vmstat – Display slab info

Use option -m, to display the slab info as shown below.
$ vmstat -m
Cache                       Num  Total   Size  Pages
fib6_nodes                    5    113     32    113
ip6_dst_cache                 4     15    256     15
ndisc_cache                   1     15    256     15
RAWv6                         7     10    768      5
UDPv6                         0      0    640      6
tw_sock_TCPv6                 0      0    128     30
...

6. vmstat – Display statistics in a table format

Instead of displays the values in the record format, you can display the output of vmstat in table format using option -s as shown below.
$ vmstat -s
      4149928  total memory
      3864824  used memory
      2606664  active memory
      1098180  inactive memory
       285104  free memory
        19264  buffer memory
      2326692  swap cache
      4192956  total swap
       274872  used swap
      3918084  free swap
   1032454000 non-nice user cpu ticks
        14568 nice user cpu ticks
     89482270 system cpu ticks
  16674327143 idle cpu ticks
    368965706 IO-wait cpu ticks
      1180468 IRQ cpu ticks
..

7. vmstat – Display disk statistics

Use option -d to display the disk statistics as shown below. This displays the reads, writes, and I/O statistics of the disk.
$ vmstat -d
disk- ------------reads------------ ------------writes----------- -----IO------
       total merged sectors      ms  total merged sectors      ms    cur    sec
sda   153189971 69093708 2719150864 737822879 329617713 157559204 3965687592 4068577985      0 1102243
sdb   501426305 97099356 2345472425 731613156 419220973 533565961 2661869460 1825174087      0 1510434
sdc   884213459 22078974 513390701 452540172 127474901 8993357 2411187300 2133226954      0 1569758

8. vmstat – Increase the width of the display

The default output without increasing the width is shown below.
$ vmstat 1 3
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  0      0 3608688 148368 3898204    0    0     0     0    1    1  0  0 100  0  0
 0  0      0 3608804 148368 3898204    0    0     0     0   72   30  0  0 100  0  0
 0  0      0 3608804 148368 3898204    0    0     0     0   60   27  0  0 100  0  0
Use option -w to increase the width of the output columns as shown below. This give better readability.
$ vmstat -w 1 3
procs -------------------memory------------------ ---swap-- -----io---- --system-- -----cpu-------
 r  b       swpd       free       buff      cache   si   so    bi    bo   in   cs  us sy  id wa st
 0  0          0    3608712     148368    3898204    0    0     0     0    1    1   0  0 100  0  0
 0  0          0    3608712     148368    3898204    0    0     0     0   93   23   0  0 100  0  0
 0  0          0    3608696     148368    3898204    0    0     0     0   35   34   0  0 100  0  0

9. vmstat – Display statistics for a partition

To display the disk I/O statistics of a specific disk partition use option -p as shown below.
$ vmstat -p sdb1
sdb1          reads   read sectors  writes    requested writes
           501423248 2345417917  419221612 2661885948

10. vmstat – Display in MB

By default vmstat displays the memory information in kb. To disply in MB, use the option “-S m” as shown below.

$ vmstat -S m
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  0    281    288     19   2386    0    0     4     1    0    0  6  1 92  2  0


 

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