NAME

vmstat - 報告虛擬內存的統計信息  

總覽

vmstat [-n] [延時[次數]]
vmstat [-V]  

描述

vmstat 對系統的進程情況、內存使用情況、交換頁和 I/O 塊使用情況、中斷以及 CPU 使用情況進行統計并報告相應的信息。

第一個顯示內容指出了計算機自上次重啟至今的平均使用情況。后面的每一行信息是按 延時 定期地顯示系統的各部分信息。進程信息和內存信息都是即時產生的。

選項

-n 開關令第一次的信息只顯示一次而不是周期地產生。

延時 是以秒為單位的刷新時間間隔。如果沒有給出此延時時間，則僅顯示系統啟動至今的平均值。

次數 指的是更新的次數。如果沒有指定此數而又定義了延時時間，則次數的默認值是無窮次。

-V 開關可以用來輸出該命令的版本信息。  

輸出信息簡介

Procs

r: 等待運行的進程數 b: 處在非中斷睡眠狀態的進程數 w: 被交換出去的可運行的進程數。此數由 linux 計算得出，但 linux 并不耗盡交換空間

Memory

swpd: 虛擬內存使用情況，單位：KB
free: 空閑的內存，單位KB
buff: 被用來做為緩存的內存數，單位：KB

Swap

si: 從磁盤交換到內存的交換頁數量，單位：KB/秒
so: 從內存交換到磁盤的交換頁數量，單位：KB/秒

IO

bi: 發送到塊設備的塊數，單位：塊/秒
bo: 從塊設備接收到的塊數，單位：塊/秒

System

in: 每秒的中斷數，包括時鐘中斷
cs: 每秒的環境（上下文）切換次數

CPU

按 CPU 的總使用百分比來顯示

us: CPU 使用時間
sy: CPU 系統使用時間
id: 閑置時間

注意

運行 vmstat 不須要特別的使用權限

這些系統信息是用來向用戶提供分析系統瓶頸問題信息的。 linux在計算進程情況時不將正在運行的 vmstat 自己計算進去。

當前所在的 linux 塊的大小都是 1K，而 CD-ROM 文件系統的塊大小為 2K。  

相關文件

/proc/meninfo
/proc/stat
/proc/*/stat

又見

ps(1),top(1),free(1)  

#p#

NAME

vmstat - Report virtual memory statistics  

SYNOPSIS

vmstat [-a] [-n] [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 -m 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, shown as zero.



 
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)