vmstat(1) General Commands Manual vmstat(1)
vmstat - report virtual memory statistics
vmstat [ interval [ count ] ]
vmstat -v [ interval [ count ] ]
vmstat -Kks namelist [ corefile ]
The command reports statistics on processes, virtual memory, disk, trap, and cpu activity.
If is specified without arguments, this command summarizes the virtual memory activity since the system was last booted. If the interval
argument is specified, then successive lines are summaries of activity over the last interval seconds. Because many statistics are sampled
in the system every five seconds, five is a good specification for interval; other statistics vary every second. If the count argument is
provided, the statistics are repeated count times.
When you run the format fields are as follows:
Procs: information about numbers of processes in various states.
r in run queue
b blocked for resources (i/o, paging, and so on.)
w runnable or short sleeper (< 20 seconds) but swapped
faults: trap/interrupt rate averages per second over the last 5 seconds.
in (non clock) device interrupts per second
sy system calls per second
cs cpu context switch rate (switches/second)
cpu: breakdown of percentage usage of cpu time
us user time for normal and low priority processes
sy system time
id cpu idle time
Memory: information about the use 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.
avm active virtual pages
fre size of the free list
Pages are reported in units of 1024 bytes.
If the number of pages exceeds 9999, it is shown in a scaled representation. The suffix k indicates multiplication by 1000 and the suffix
m indicates multiplication by 1000000. For example, the value 12345 appears as 12k.
page: information about page faults and paging activity. These are averaged every five seconds, and given in units per second. The size
of a unit is always 1024 bytes and is independent of the actual page size on a machine.
re page reclaims (simulating reference bits)
at pages attached (found in free list not swapdev or filesystem)
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
disk: s0, s1 ...sn: Paging/swapping disk sector transfers per second (this field is system dependent). Typically paging is split across
several of the available drives. This will print for each paging/swapping device configured into the kernel.
-f Provides 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.
-K Displays usage statistics of the kernel memory allocator.
-k Allows a dump to be interrogated to print the contents of the sum structure when specified with a namelist and corefile. This is
-S Replaces the page reclaim (re) and pages attached (at) fields with processes swapped in (si) and processes swapped out (so).
-s Prints the contents of the sum structure, giving the total number of several kinds of paging related events that have occurred since
-v Prints an expanded form of the virtual memory statistics.
-z Zeroes out the sum structure if the UID indicates root privilege.
The following command prints what the system is doing every five seconds:
To find the status after a core dump use the following:
vmstat -k vmunix.? vmcore.?