NAME
vmstat - 报告虚拟内存的统计信息
总览
vmstat [-n] [延时[次数]]
vmstat [-V]
描述
vmstat 对系统的进程情况、内存使用情况、交换页和 I/O 块使用情况、中断以及 CPU 使用情况进行统计并报告相应的信息。
第一个显示内容指出了计算机自上次重启至今的平均使用情况。后面的每一行信息是按 延时 定期地显示系统的各部分信息。进程信息和内存信息都是即时产生的。
选项
-n 开关令第一次的信息只显示一次而不是周期地产生。
延时 是以秒为单位的刷新时间间隔。如果没有给出此延时时间，则仅显示系统启动至今的平均值。
次数 指的是更新的次数。如果没有指定此数而又定义了延时时间，则次数的默认值是无穷次。
-V 开关可以用来输出该命令的版本信息。
输出信息简介
Procs
r: 等待运行的进程数 b: 处在非中断睡眠状态的进程数 w: 被交换出去的可运行的进程数。此数由 linux 计算得出，但 linux 并不耗尽交换空间
Memory
swpd: 虚拟内存使用情况，单位：KB free: 空闲的内存，单位KB buff: 被用来做为缓存的内存数，单位：KB
Swap
si: 从磁盘交换到内存的交换页数量，单位：KB/秒 so: 从内存交换到磁盘的交换页数量，单位：KB/秒
IO
bi: 发送到块设备的块数，单位：块/秒 bo: 从块设备接收到的块数，单位：块/秒
System
in: 每秒的中断数，包括时钟中断 cs: 每秒的环境（上下文）切换次数
CPU
按 CPU 的总使用百分比来显示
us: CPU 使用时间 sy: CPU 系统使用时间 id: 闲置时间
注意
运行 vmstat 不须要特别的使用权限
这些系统信息是用来向用户提供分析系统瓶颈问题信息的。 linux在计算进程情况时不将正在运行的 vmstat 自己计算进去。
当前所在的 linux 块的大小都是 1K，而 CD-ROM 文件系统的块大小为 2K。
相关文件
/proc/meninfo /proc/stat /proc/*/stat
又见
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 readingWrites
total: Total writes completed successfully merged: grouped writes (resulting in one I/O) sectors: Sectors written successfully ms: milliseconds spent writingIO
cur: I/O in progress s: seconds spent for I/OFIELD 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 partitionFIELD 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 slabNOTES
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/*/statSEE ALSO
iostat(1), sar(1), mpstat(1), ps(1), top(1), free(1)
