VMSTAT(1) VMSTAT(1)
NAME
vmstat - report virtual memory statistics
SYNOPSIS
vmstat [-ms] [-c count] [-w wait] [-M core] [-N system] [disks]
DESCRIPTION
Vmstat reports certain kernel statistics kept about pro-
cess, virtual memory, disk, trap and cpu activity.
The options are as follows:
-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.
-w Pause wait seconds between each display. If no
repeat count is specified, the default is infinity.
-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 dis-
play. If no wait interval is specified, the
default is 1 second.
-M Extract values associated with the name list from
the specified kernel core file. This is not cur-
rently implemented.
-N For the purpose of analyzing dead kernels, extract
symbol information from the named file. This is
not currently implemented.
By default, vmstat displays the following information:
procs Information about the numbers of processes in vari-
ous 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 pro-
cesses which are running or have run in the last 20
seconds.
avm active virtual pages
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VMSTAT(1) VMSTAT(1)
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 config-
ured 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 -w 5'' will print what the system is
doing every five seconds; this is a good choice of print-
ing interval since this is how often some of the statis-
tics 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.
SEE ALSO
fstat(1), netstat(1), nfsstat(1), ps(1), systat(1),
iostat(8), pstat(8)
The sections starting with ``Interpreting system activ-
ity'' in Installing and Operating 4.3BSD.
BUGS
The -c and -w options are only available with the default
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VMSTAT(1) VMSTAT(1)
output.
The current implementation recovers statistics using sys-
tem calls to the running kernel. There is no support for
simulating the system calls on dead kernels yet.
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