statistics about kernel activities
reports certain kernel statistics kept about
process, virtual memory, disk, trap, and CPU activity. The default behavior is
to print a one-line summary of these statistics. The
be used to continually report summaries.
The options are as follows:
- 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.
- Report on the number of
vfork(2) system calls as well
as kernel thread creations since system startup, and the number of pages
of virtual memory involved in each.
- Report on the number of interrupts taken by each device
since system startup.
- Extract values associated with the name list from the
specified core instead of the running kernel.
- Report on the usage of kernel dynamic memory listed first
by size of allocation and then by type of usage.
- Extract the name list from the specified system instead of
the running kernel.
- Display the contents of the
uvmexp structure (see
uvm(9)), giving the total
number of several kinds of paging related events which have occurred since
- Report on the number of page in and page reclaims since
system startup, and the amount of time required by each.
- Print more verbose information.
- Pause wait seconds between
each display. If no repeat count is
specified, the default is infinity.
- When used with -i, also list
devices which have not yet generated an interrupt.
By default, vmstat
displays the following
information just once:
- Information about the numbers of processes in various
- in run queue
- Information about the usage of virtual and real memory.
- active virtual pages
- size of the free list
- Information about page faults and paging activity. These
are averaged each five seconds, and given in units per second.
- page faults
- page reclaims (simulating reference bits)
- pages paged in
- pages paged out
- pages freed
- pages scanned by clock algorithm
- Disk transfers per second. 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 two disk
drives are configured in the system, vmstat
displays only the first two drives. To force
vmstat to display specific drives, their
names may be supplied on the command line.
- Trap/interrupt rate averages per second over last 5
- device interrupts per interval (including clock
- system calls per interval
- CPU context switch rate (switches/interval)
- Breakdown of percentage usage of CPU time.
- user time for normal and low priority processes
- system time
- CPU idle
- default kernel image
- default memory file
The command vmstat -w 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.
are only available with the default output.
This manual page lacks an incredible amount of detail.