VMSTAT

Section: User Commands (1)
Updated: June 20, 1991
Index Return to Main Contents
 

NAME

vmstat - report virtual memory statistics  

SYNOPSIS

vmstat [ -fimst ] [ -c count ] [ -M core ] [ -N system ]


     [ -w wait ] [ disks ]
 

DESCRIPTION

Vmstat reports certain kernel statistics kept about process, virtual memory, disk, trap and cpu activity.

The options are as follows:

-c
Repeat the display count times. The first display is for the time since a reboot and each subsequent report is for the time period since the last display. If no wait interval is specified, the default is 1 second.
-f
Report on the number fork(2) and vfork(2) system calls since system startup, and the number of pages of virtual memory involved in each.
-i
Report on the number of interrupts taken by each device since system startup.
-M
Extract values associated with the name list from the specified core instead of the default ``/dev/kmem''.
-N
Extract the name list from the specified system instead of the default ``/vmunix''.
-m
Report on the usage of kernel dynamic memory listed first by size of allocation and then by type of usage.
-s
Display the contents of the sum structure, giving the total number of several kinds of paging related events which have occurred since system startup.
-t
Report on the number of page in and page reclaims since system startup, and the amount of time required by each.
-w
Pause wait seconds between each display. If no repeat count is specified, the default is infinity.

By default, vmstat displays the following information:

procs
Information about the numbers of processes in various states. 

r       in run queue
b       blocked for resources (i/o, paging, etc.)
w       runnable or short sleeper (< 20 secs) but swapped
memory
Information about the usage of virtual and real memory. Virtual pages (reported in units of 1024 bytes) are considered active if they belong to processes which are running or have run in the last 20 seconds. 

avm     active virtual pages
fre     size of the free list
page
Information about page faults and paging activity. These are averaged each five seconds, and given in units per second. 

re      page reclaims (simulating reference bits)
at      pages attached (found in free list)
pi      pages paged in
po      pages paged out
fr      pages freed per second
de      anticipated short term memory shortfall
sr      pages scanned by clock algorithm, per-second
disks
Disk operations per second (this field is system dependent). Typically paging will be split across the available drives. The header of the field is the first character of the disk name and the unit number. If more than four disk drives are configured in the system, vmstat displays only the first four drives. To force vmstat to display specific drives, their names may be supplied on the command line.
faults
Trap/interrupt rate averages per second over last 5 seconds. 

in      device interrupts per interval (including clock interrupts)
sy      system calls per interval
cs      cpu context switch rate (switches/interval)
cpu
Breakdown of percentage usage of CPU time. 

us      user time for normal and low priority processes
sy      system time
id      cpu idle
 

EXAMPLES

The command ``vmstat -i 5'' will print what the system is doing every five seconds; this is a good choice of printing interval since this is how often some of the statistics are sampled in the system. Others vary every second and running the output for a while will make it apparent which are recomputed every second.  

FILES

/vmunix    default kernel namelist

/dev/kmem default memory file
 

SEE ALSO

fstat(1), netstat(1), nfsstat(1), ps(1), systat(1), iostat(8), pstat(8)

The sections starting with ``Interpreting system activity'' in Installing and Operating 4.3BSD.  

BUGS

The -c and -w options are only available with the default output.

 

Index

NAME
SYNOPSIS
DESCRIPTION
EXAMPLES
FILES
SEE ALSO
BUGS
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