# vmstat

## NAME



           vmstat - Report virtual memory statistics
    


## SYNOPSIS



           **vmstat**[_option_ ...] [_delay_ [_count_]]
    


## DESCRIPTION



           **vmstat** reports information about processes, memory, paging, block
           IO, traps, disks 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



           _delay_  The _delay_ between updates in seconds.  If no _delay_ is
                  specified, only one report is printed with the average
                  values since boot.
    
           _count_  Number of updates.  In absence of _count_ , when _delay_ is
                  defined, default is infinite.
    
           **-a** , **--active**
                  Display active and  inactive memory, given a 2.5.41 kernel
                  or better.
    
           **-f** , **--forks**
                  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.
    
           **-m** , **--slabs**
                  Displays slabinfo.
    
           **-n** , **--one-header**
                  Display the header only once rather than periodically.
    
           **-s** , **--stats**
                  Displays a table of various event counters and memory
                  statistics.  This display does not repeat.
    
           **-d** , **--disk**
                  Report disk statistics (2.5.70 or above required).
    
           **-D** , **--disk-sum**
                  Report some summary statistics about disk activity.
    
           **-p** , **--partition** _device_
                  Detailed statistics about partition (2.5.70 or above
                  required).
    
           **-S** , **--unit** _character_
                  Switches outputs between 1000 (_k_), 1024 (_K_), 1000000 (_m_),
                  or 1048576 (_M_) bytes.  Note this does not change the block
                  (bi/bo) fields.
    
           **-t** , **--timestamp**
                  Append timestamp to each line
    
           **-w** , **--wide**
                  Wide output mode (useful for systems with higher amount of
                  memory, where the default output mode suffers from unwanted
                  column breakage).  The output is wider than 80 characters
                  per line.
    
           **-y** , **--no-first**
                  Omits first report with statistics since system boot.
    
           **-V** , **--version**
                  Display version information and exit.
    
           **-h** , **--help**
                  Display help and exit.
    


## FIELD DESCRIPTION FOR VM MODE



       **Procs**
           r: The number of runnable processes (running or waiting for run time).
           b: The number of processes blocked waiting for I/O to complete.
    
       **Memory**
           These are affected by the **--unit** option.
           swpd: the amount of swap 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**
           These are affected by the **--unit** option.
           si: Amount of memory swapped in from disk (/s).
           so: Amount of memory swapped to disk (/s).
    
       **IO**
           bi: Kibibyte received from a block device (KiB/s).
           bo: Kibibyte sent to a block device (KiB/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: 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.
           gu: Time spent running KVM guest code (guest time, including guest nice).
    


## 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



           Slab mode shows statistics per slab, for more information about
           this information see slabinfo(5)
    
           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
    


## NOTES



           **vmstat** requires read access to files under _/proc_. The **-m** requires
           read access to _/proc/slabinfo_ which may not be available to
           standard users.  Mount options for _/proc_ such as _subset=pid_ may
           also impact what is visible.
    


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