vmstat(8) [redhat man page]
VMSTAT(8) Linux Administrator's Manual VMSTAT(8) NAME
vmstat - Report virtual memory statistics SYNOPSIS
vmstat [-n] [delay [ count]] vmstat[-V] DESCRIPTION
vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity. The first report produced gives averages since the last reboot. Additional reports give information on a sampling period of length delay. The process and memory reports are instantaneous in either case. Options The -n switch causes the header to be displayed only once rather than periodically. delay is the delay between updates in seconds. If no delay is specified, only one report is printed with the average values since boot. count is the number of updates. If no count is specified and delay is defined, count defaults to infinity. The -V switch results in displaying version information. FIELD DESCRIPTIONS
Procs r: The number of processes waiting for run time. b: The number of processes in uninterruptable sleep. w: The number of processes swapped out but otherwise runnable. This field is calculated, but Linux never desperation swaps. Memory swpd: the amount of virtual memory used (kB). free: the amount of idle memory (kB). buff: the amount of memory used as buffers (kB). Swap si: Amount of memory swapped in from disk (kB/s). so: Amount of memory swapped to disk (kB/s). IO bi: Blocks sent to a block device (blocks/s). bo: Blocks received from a block device (blocks/s). System in: The number of interrupts per second, including the clock. cs: The number of context switches per second. CPU These are percentages of total CPU time. us: user time sy: system time id: idle time NOTES
vmstat does not require special permissions. These reports are intended to help identify system bottlenecks. Linux vmstat does not count itself as a running process. All linux blocks are currently 1k, except for CD-ROM blocks which are 2k. FILES
/proc/meminfo /proc/stat /proc/*/stat SEE ALSO
ps(1), top(1), free(1) BUGS
Does not tabulate the block io per device or count the number of system calls. AUTHOR
Written by Henry Ware <al172@yfn.ysu.edu>. Throatwobbler Ginkgo Labs 27 July 1994 VMSTAT(8)
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vmstat(1) General Commands Manual vmstat(1) Name vmstat - report virtual memory statistics Syntax vmstat [ interval [ count ] ] vmstat -v [ interval [ count ] ] vmstat -fKSsz vmstat -Kks namelist [ corefile ] Description 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. Options -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 the default. -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 boot. -v Prints an expanded form of the virtual memory statistics. -z Zeroes out the sum structure if the UID indicates root privilege. Examples The following command prints what the system is doing every five seconds: vmstat 5 To find the status after a core dump use the following: cd /usr/adm/crash vmstat -k vmunix.? vmcore.? Files Kernel memory System namelist vmstat(1)