Linux performance monitoring with vmstat and iostat commands

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This is our ongoing series of Linux commands and Linux performance monitors. You can learn more about it in this article Vmstat and Iostat Commands common to all Unix-like (Linux / Unix / FreeBSD / Solaris) Operating systems.

vmstat Command (also known as the virtual memory statistics tool) displays information about processes, memory, disk and CPU activity in Linux during the iostat The command is used to monitor CPU usage and system input / output statistics for all hard drives and partitions.

When vmstat and iostat Commands are not available on your Linux computer, please install the sysstat Package. the vmstat, Mister, and iostat Commands are the collection of packages contained in sysstat – the system monitoring tools.

You can download and install sysstat Using Link’s source tarball sysstat, but we recommend installing through the package manager.

Install Sysstat on Linux

$ sudo apt install sysstat         [On Debian, Ubuntu and Mint]
$ sudo yum install sysstat         [On RHEL/CentOS/Fedora and Rocky Linux/AlmaLinux]
$ sudo emerge -a app-admin/sysstat [On Gentoo Linux]
$ sudo pacman -S sysstat           [On Arch Linux]
$ sudo zypper install sysstat      [On OpenSUSE]    
Install Sysstat on Linux

Learn Vmstat command examples in Linux

In this section you will learn 6 examples of vmstat commands and use with screenshots.

1. List active and inactive storage

There are six columns in the following example. The meaning of the columns is given in the man page for. explained vmstat in detail. The most important fields are for free under memory and si, well under the swap column.

[[email protected] ~]# 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
 1  0      0 810420  97380  70628    0    0   115     4   89   79  1  6 90  3  0
  • For free – Number of free / unused storage spaces.
  • and – Exchanged from the hard drive to kilobytes every second.
  • So – Swapped out to the hard drive every second in kilobytes.

Note: When you run vmstat without parameters, a summary report is displayed since the system was started.

2. Run vmstat ‘X’ seconds and (‘number)

With this command vmstat run every two seconds and stop automatically after six intervals.

[[email protected] ~]# vmstat 2 6

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 810420  22064 101368    0    0    56     3   50   57  0  3 95  2  0
 0  0      0 810412  22064 101368    0    0     0     0   16   35  0  0 100  0  0
 0  0      0 810412  22064 101368    0    0     0     0   14   35  0  0 100  0  0
 0  0      0 810412  22064 101368    0    0     0     0   17   38  0  0 100  0  0
 0  0      0 810412  22064 101368    0    0     0     0   17   35  0  0 100  0  0
 0  0      0 810412  22064 101368    0    0     0     0   18   36  0  1 100  0  0

3. Vmstat with timestamps

vmstat Command with -t Parameter displays timestamp with each line printed as shown below.

[[email protected] ~]$ vmstat -t 1 5

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 632028  24992 192244    0    0    70     5   55   78  1  3 95  1  0        2012-09-02 14:57:18 IST
 1  0      0 632028  24992 192244    0    0     0     0  171  514  1  5 94  0  0        2012-09-02 14:57:19 IST
 1  0      0 631904  24992 192244    0    0     0     0  195  600  0  5 95  0  0        2012-09-02 14:57:20 IST
 0  0      0 631780  24992 192244    0    0     0     0  156  524  0  5 95  0  0        2012-09-02 14:57:21 IST
 1  0      0 631656  24992 192244    0    0     0     0  189  592  0  5 95  0  0        2012-09-02 14:57:22 IST

4. Statistics of various counters

vmstat Command with -s The switch shows a summary of various event counters and memory statistics.

[[email protected] ~]$ vmstat -s

      1030800  total memory
       524656  used memory
       277784  active memory
       185920  inactive memory
       506144  free memory
        26864  buffer memory
       310104  swap cache
      2064376  total swap
            0  used swap
      2064376  free swap
         4539 non-nice user cpu ticks
            0 nice user cpu ticks
        11569 system cpu ticks
       329608 idle cpu ticks
         5012 IO-wait cpu ticks
           79 IRQ cpu ticks
           74 softirq cpu ticks
            0 stolen cpu ticks
       336038 pages paged in
        67945 pages paged out
            0 pages swapped in
            0 pages swapped out
       258526 interrupts
       392439 CPU context switches
   1346574857 boot time
         2309 forks

5. Monitor Linux hard drive statistics

vmstat With -d Option shows all hard drive statistics from Linux.

[[email protected] ~]$ vmstat -d

disk- ------------reads------------ ------------writes----------- -----IO------
       total merged sectors      ms  total merged sectors      ms    cur    sec
ram0       0      0       0       0      0      0       0       0      0      0
ram1       0      0       0       0      0      0       0       0      0      0
ram2       0      0       0       0      0      0       0       0      0      0
ram3       0      0       0       0      0      0       0       0      0      0
ram4       0      0       0       0      0      0       0       0      0      0
ram5       0      0       0       0      0      0       0       0      0      0
ram6       0      0       0       0      0      0       0       0      0      0
ram7       0      0       0       0      0      0       0       0      0      0
ram8       0      0       0       0      0      0       0       0      0      0
ram9       0      0       0       0      0      0       0       0      0      0
ram10      0      0       0       0      0      0       0       0      0      0
ram11      0      0       0       0      0      0       0       0      0      0
ram12      0      0       0       0      0      0       0       0      0      0
ram13      0      0       0       0      0      0       0       0      0      0
ram14      0      0       0       0      0      0       0       0      0      0
ram15      0      0       0       0      0      0       0       0      0      0
loop0      0      0       0       0      0      0       0       0      0      0
loop1      0      0       0       0      0      0       0       0      0      0
loop2      0      0       0       0      0      0       0       0      0      0
loop3      0      0       0       0      0      0       0       0      0      0
loop4      0      0       0       0      0      0       0       0      0      0
loop5      0      0       0       0      0      0       0       0      0      0
loop6      0      0       0       0      0      0       0       0      0      0
loop7      0      0       0       0      0      0       0       0      0      0
sr0        0      0       0       0      0      0       0       0      0      0
sda     7712   5145  668732  409619   3282  28884  257402  644566      0    126
dm-0   11578      0  659242 1113017  32163      0  257384 8460026      0    126
dm-1     324      0    2592    3845      0      0       0       0      0      2

6. View statistics in megabytes

the vmstat shows memory statistics in kilobytes by default, but you can also use the argument to show reports with memory sizes in megabytes -S M. Consider the following example.

[[email protected] ~]# vmstat -S M 1 5

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    346     53    476    0    0    95     8   42   55  0  2 96  2  0
 0  0      0    346     53    476    0    0     0     0   12   15  0  0 100  0  0
 0  0      0    346     53    476    0    0     0     0   32   62  0  0 100  0  0
 0  0      0    346     53    476    0    0     0     0   15   13  0  0 100  0  0
 0  0      0    346     53    476    0    0     0     0   34   61  0  1 99  0  0

Learn Iostat command examples in Linux

In this section you will learn 6 examples of iostat commands and their use with screenshots.

7. View CPU and I / O statistics for hard drives

iostat shows without arguments Central processor and I / O Statistics of all partitions as shown below.

[[email protected] ~]# iostat

Linux 2.6.32-279.el6.i686 (tecmint.com)         09/03/2012      _i686_  (1 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.12    0.01    1.54    2.08    0.00   96.24

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda               3.59       161.02        13.48    1086002      90882
dm-0              5.76       159.71        13.47    1077154      90864
dm-1              0.05         0.38         0.00       2576          0

8. Displays Linux CPU statistics

iostat With -c Arguments are only displayed Central processor Statistics as shown below.

[[email protected] ~]# iostat -c

Linux 2.6.32-279.el6.i686 (tecmint.com)         09/03/2012      _i686_  (1 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.12    0.01    1.47    1.98    0.00   96.42

9. Displays I / O statistics for Linux hard drives

iostat With -d Arguments indicate media only I / O Statistics of all partitions as shown.

[[email protected] ~]# iostat -d

Linux 2.6.32-279.el6.i686 (tecmint.com)         09/03/2012      _i686_  (1 CPU)

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda               3.35       149.81        12.66    1086002      91746
dm-0              5.37       148.59        12.65    1077154      91728
dm-1              0.04         0.36         0.00       2576          0

10. Displays I / O statistics for specific devices

By default it shows statistics of all partitions, with -p and device name arguments show hard drives only I / O Statistics only for a specific device as shown.

[[email protected] ~]# iostat -p sda

Linux 2.6.32-279.el6.i686 (tecmint.com)         09/03/2012      _i686_  (1 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.11    0.01    1.44    1.92    0.00   96.52

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda               3.32       148.52        12.55    1086002      91770
sda1              0.07         0.56         0.00       4120         18
sda2              3.22       147.79        12.55    1080650      91752

11. View LVM statistics

With -N Parameter displays only (capital letters) LVM Statistics as shown.

[[email protected] ~]# iostat -N

Linux 2.6.32-279.el6.i686 (tecmint.com)         09/03/2012      _i686_  (1 CPU)

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.11    0.01    1.39    1.85    0.00   96.64

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda               3.20       142.84        12.16    1086002      92466
vg_tecmint-lv_root     5.13       141.68        12.16    1077154      92448
vg_tecmint-lv_swap     0.04         0.34         0.00       2576          0

12. Check the iostat version

With -V (Uppercase) parameter display version of iostat as shown.

[[email protected] ~]# iostat -V

sysstat version 11.7.3
(C) Sebastien Godard (sysstat  orange.fr)

the vmstat and iostat contain a number of columns and flags that may not be explained in detail. If you want to know more about it, you can refer to the man page of vmstat and iostat.

# man vmstat
# man iostat

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