VMSTAT(1) General Commands Manual VMSTAT(1)
vmstat - report virtual memory statistics
vmstat [ -fsi ] [ drives ] [ interval [ count ] ]
Vmstat delves into the system and normally reports certain statistics kept about process, virtual memory, disk, trap and cpu activity. If
given a -f argument, it instead reports on the number of forks and vforks since system startup and the number of pages of virtual memory
involved in each kind of fork. If given a -s argument, it instead prints the contents of the sum structure, giving the total number of
several kinds of paging related events which have occurred since boot. If given a -i argument, it instead reports on the number of inter-
rupts taken by each device since system startup.
If none of these options are given, vmstat will report in the first line a summary of the virtual memory activity since the system has been
booted. If interval is specified, then successive lines are summaries over the last interval seconds. ``vmstat 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, running the output for a while will make it apparent which are recomputed every second. If a
count is given, the statistics are repeated count times. The format fields are:
Procs: information about 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 are considered active if they belong to processes which are
running or have run in the last 20 seconds. A ``page'' here is 1024 bytes.
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
up/hp/rk/ra: Disk operations per second (this field is system dependent). Typically paging will be split across several of the available
drives. The number under each of these is the unit number.
Faults: trap/interrupt rate averages per second over last 5 seconds.
in (non clock) device interrupts per second
sy system calls per second
cs cpu context switch rate (switches/sec)
Cpu: breakdown of percentage usage of CPU time
us user time for normal and low priority processes
sy system time
id cpu idle
If more than 4 disk drives are configured in the system, vmstat displays only the first 4 drives, with priority given to Massbus disk
drives (i.e. if both Unibus and Massbus drives are present and the total number of drives exceeds 4, then some number of Unibus drives will
not be displayed in favor of the Massbus drives). To force vmstat to display specific drives, their names may be supplied on the command
The sections starting with ``Interpreting system activity'' in Installing and Operating 4.2bsd.
4th Berkeley Distribution March 15, 1986 VMSTAT(1)