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.\"	@(#)vmstat.8	6.8 (Berkeley) 6/20/91
.\"
.TH VMSTAT 1 "June 20, 1991"
.UC 4
.SH NAME
vmstat \- report virtual memory statistics
.SH SYNOPSIS
.nf
.ft B
vmstat [ \-fimst ] [ \-c count ] [ \-M core ] [ \-N system ]
.ti +5
[ \-w wait ] [ disks ]
.ft R
.fi
.SH DESCRIPTION
.I Vmstat
reports certain kernel statistics kept about process, virtual memory,
disk, trap and cpu activity.
.PP
The options are as follows:
.TP
\-c
Repeat the display
.I 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
.I wait
interval is specified, the default is 1 second.
.TP
\-f
Report on the number
.IR fork (2)
and
.IR vfork (2)
system calls since system startup, and the number of pages of virtual memory
involved in each.
.TP
\-i
Report on the number of interrupts taken by each device since system
startup.
.TP
\-M
Extract values associated with the name list from the specified core 
instead of the default ``/dev/kmem''.
.TP
\-N
Extract the name list from the specified system instead of the default
``/vmunix''.
.TP
\-m
Report on the usage of kernel dynamic memory listed first by size of
allocation and then by type of usage.
.TP
\-s
Display the contents of the
.I sum
structure, giving the total number of several kinds of paging related
events which have occurred since system startup.
.TP
\-t
Report on the number of page in and page reclaims since system startup,
and the amount of time required by each.
.TP
\-w
Pause
.I wait
seconds between each display.
If no repeat
.I count
is specified, the default is infinity.
.PP
By default,
.I vmstat
displays the following information:
.PP
.TP
procs
Information about the numbers of processes in various states.
.sp
.RS
.nf
r	in run queue
b	blocked for resources (i/o, paging, etc.)
w	runnable or short sleeper (< 20 secs) but swapped
.fi
.RE
.TP
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.
.sp
.RS
.nf
avm	active virtual pages
fre	size of the free list
.fi
.RE
.TP
page
Information about page faults and paging activity.
These are averaged each five seconds, and given in units per second.
.sp
.RS
.nf
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
.fi
.RE
.TP
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,
.I vmstat
displays only the first four drives.
To force
.I vmstat
to display specific drives, their names may be supplied on the command line.
.TP
faults
Trap/interrupt rate averages per second over last 5 seconds.
.sp
.RS
.nf
in	device interrupts per interval (including clock interrupts)
sy	system calls per interval
cs	cpu context switch rate (switches/interval)
.fi
.RE
.TP
cpu
Breakdown of percentage usage of CPU time.
.sp
.RS
.nf
us	user time for normal and low priority processes
sy	system time
id	cpu idle
.fi
.RE
.SH 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.
.SH FILES
.ta \w'/dev/kmem  'u
/vmunix	default kernel namelist
.br
/dev/kmem	default memory file
.SH SEE ALSO
.IR fstat (1),
.IR netstat (1),
.IR nfsstat (1),
.IR ps (1),
.IR systat (1),
.IR iostat (8),
.IR pstat (8)
.sp
The sections starting with ``Interpreting system activity'' in
.IR "Installing and Operating 4.3BSD" .
.SH BUGS
The \-c and \-w options are only available with the default output.