-a

Display active and inactive memory, given a 2.5.41 kernel or better.

-f

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

-m

Displays slabinfo.

-n

Display the header only once rather than periodically.

-s

Displays a table of various event counters and memory statistics. This display does not repeat.

-d

Report disk statistics (2.5.70 or above required).

-D

Report some summary statistics about disk activity.

-p

Detailed statistics about partition (2.5.70 or above required).

-S

Switches outputs between 1000 (k), 1024 (K), 1000000 (m), or 1048576 (M) bytes. Note this does notchange the swap (si/so) or block (bi/bo) fields.

-t

Append timestamp to each line

-w

Wide output mode (useful for systems with higher amount of memory, where the default output mode suf‐fers from unwanted column breakage). The output is wider than 80 characters per line.

-V

Display version information and exit.

-h

Display help and exit.FIELD DESCRIPTION FOR VM MODEProcsr: The number of runnable processes (running or waiting for run time).b: The number of processes in uninterruptible sleep.Memoryswpd: 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)Swapsi: Amount of memory swapped in from disk (/s).so: Amount of memory swapped to disk (/s).IObi: Blocks received from a block device (blocks/s).bo: Blocks sent to a block device (blocks/s).Systemin: The number of interrupts per second, including the clock.cs: The number of context switches per second.CPUThese 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 MODEReadstotal: Total reads completed successfullymerged: grouped reads (resulting in one I/O)sectors: Sectors read successfullyms: milliseconds spent readingWritestotal: Total writes completed successfullymerged: grouped writes (resulting in one I/O)sectors: Sectors written successfullyms: milliseconds spent writingIOcur: I/O in progresss: seconds spent for I/OFIELD DESCRIPTION FOR DISK PARTITION MODEreads: Total number of reads issued to this partitionread sectors: Total read sectors for partitionwrites : Total number of writes issued to this partitionrequested writes: Total number of write requests made for partitionFIELD DESCRIPTION FOR SLAB MODEcache: Cache namenum: Number of currently active objectstotal: Total number of available objectssize: Size of each objectpages: Number of pages with at least one active objectNOTESvmstat does not require special permissions.These reports are intended to help identify system bottlenecks. Linux vmstat does not count itself as a run‐ning process.All linux blocks are currently 1024 bytes. Old kernels may report blocks as 512 bytes, 2048 bytes, or 4096bytes.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 1.1FILES/proc/meminfo/proc/stat/proc/*/stat