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vmstat

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Langue: en

Version: 27 July 1994 (fedora - 01/12/10)

Section: 8 (Commandes administrateur)

NAME

vmstat - Report virtual memory statistics

SYNOPSIS

vmstat [-a] [-n] [-t] [delay [ count]]
vmstat [-f] [-s] [-m]
vmstat [-S unit]
vmstat [-d]
vmstat [-p disk partition]
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 -a switch displays active/inactive memory, given a 2.5.41 kernel or better.

The -f switch displays the number of forks since boot. This includes the fork, vfork, and clone system calls, and is equivalent to the total number of tasks created. Each process is represented by one or more tasks, depending on thread usage. This display does not repeat.

The -t switch adds timestamp to the output.

The -m switch displays slabinfo.

The -n switch causes the header to be displayed only once rather than periodically.

The -s switch displays a table of various event counters and memory statistics. This display does not repeat.

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 -d reports disk statistics (2.5.70 or above required)

The -p followed by some partition name for detailed statistics (2.5.70 or above required)

The -S followed by k or K or m or M switches outputs between 1000, 1024, 1000000, or 1048576 bytes

The -V switch results in displaying version information.

FIELD DESCRIPTION FOR VM MODE

Procs

 r: The number of processes waiting for run time.  
 b: The number of processes in uninterruptible sleep.
 

Memory

 swpd: the amount of virtual memory used.
 free: the amount of idle memory.
 buff: the amount of memory used as buffers.
 cache: the amount of memory used as cache.
 inact: the amount of inactive memory. (-a option)
 active: the amount of active memory. (-a option)
 

Swap

 si: Amount of memory swapped in from disk (/s).
 so: Amount of memory swapped to disk (/s).
 

IO

 bi: Blocks received from a block device (blocks/s).
 bo: Blocks sent to a block device (blocks/s).
 

System

 in: The number of interrupts per second, including the clock.
 cs: The number of context switches per second.
 
 These are percentages of total CPU time.
 

 us: Time spent running non-kernel code. (user time, including nice time)
 sy: Time spent running kernel code. (system time)
 id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
 wa: Time spent waiting for IO. Prior to Linux 2.5.41, included in idle.
 st: Time stolen from a virtual machine. Prior to Linux 2.6.11, unknown.
 
 
 
 
 

FIELD DESCRIPTION FOR DISK MODE


 
 

Reads


 
 

 total: Total reads completed successfully 
 merged: grouped reads (resulting in one I/O)
 sectors: Sectors read successfully
 ms: milliseconds spent reading
 

 
 

Writes


 
 

 total: Total writes completed successfully
 merged: grouped writes (resulting in one I/O)
 sectors: Sectors written successfully
 ms: milliseconds spent writing
 

 
 

IO


 
 

 cur: I/O in progress
 s: seconds spent for I/O
 

 
 

FIELD DESCRIPTION FOR DISK PARTITION MODE


 
 

 reads: Total number of reads issued to this partition
 read sectors: Total read sectors for partition
 writes : Total number of writes issued to this partition
 requested writes: Total number of write requests made for partition
 
 

 
 

FIELD DESCRIPTION FOR SLAB MODE


 
 

 cache: Cache name
 num: Number of currently active objects
 total: Total number of available objects
 size: Size of each object
 pages: Number of pages with at least one active object
 totpages: Total number of allocated pages
 pslab: Number of pages per slab
 

 
 

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 1024 bytes. Old kernels may report blocks as 512 bytes, 2048 bytes, or 4096 bytes.
Since procps 3.1.9, vmstat lets you choose units (k, K, m, M) default is K (1024 bytes) in the default mode
vmstat uses slabinfo 1.1 FIXME

FILES


 
 
 
 

 /proc/meminfo
 /proc/stat
 /proc/*/stat
 

 
 

SEE ALSO


 
 iostat(1), sar(1), mpstat(1), ps(1), top(1), free(1)
 

BUGS


 
 Does not tabulate the block io per device or count the number of system calls.
 

AUTHORS


 
 

 Written by Henry Ware <al172@yfn.ysu.edu>. 
 Fabian Fr'ed'erick <ffrederick@users.sourceforge.net> (diskstat, slab, partitions...)
 
 

 
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