meminfo vmstat procrank top等詳解

http://blog.csdn.net/arnoldlu/article/details/8443794

meminfo

命令：cat /proc/meminfo

例項：

MemTotal:         234312 kB

MemFree:            3448 kB

Buffers:              92 kB

Cached:            18052 kB

SwapCached:        25556 kB

Active:            50564 kB

Inactive:          50236 kB

Active(anon):      41924 kB

Inactive(anon):    41968 kB

Active(file):       8640 kB

Inactive(file):     8268 kB

Unevictable:        1164 kB

Mlocked:           17028 kB

HighTotal:             0 kB

HighFree:              0 kB

LowTotal:         234312 kB

LowFree:            3448 kB

SwapTotal:        196604 kB

SwapFree:         114384 kB

Dirty:                 0 kB

Writeback:             0 kB

AnonPages:         83900 kB

Mapped:            53944 kB

Shmem:                44 kB

Slab:              17540 kB

SReclaimable:       5828 kB

SUnreclaim:        11712 kB

KernelStack:        4184 kB

PageTables:         5304 kB

NFS_Unstable:          0 kB

Bounce:                0 kB

WritebackTmp:          0 kB

CommitLimit:      313760 kB

Committed_AS:    2792956 kB

VmallocTotal:     778240 kB

VmallocUsed:      115160 kB

VmallocChunk:     405852 kB

解釋：

MemTotal: 所有可用RAM大小 （即實體記憶體減去一些預留位和核心的二進位制程式碼大小）

    MemFree: LowFree與HighFree的總和

    Buffers: 用來給塊裝置做的緩衝大小（只記錄檔案系統的metadata以及 tracking in-flight pages，就是說 buffers是用來儲存，目錄裡面有什麼內容，許可權等等。）

    Cached: 用來給檔案做緩衝大小（直接用來記憶我們開啟的檔案）. 它不包括SwapCached

    SwapCached: 已經被交換出來的記憶體，但仍然被存放在swapfile中。用來在需要的時候很快的被替換而不需要再次開啟I/O埠。

    Active: 最近經常被使用的記憶體，除非非常必要否則不會被移作他用.

    Inactive: 最近不經常被使用的記憶體，非常用可能被用於其他途徑.

    HighTotal:
    HighFree: 高位記憶體是指所有在860MB以上的記憶體空間，該區域主要用於使用者空間的程式或者是快取頁面。核心必須使用不同的手法使用該段記憶體，因此它比低位記憶體要慢一些。

    LowTotal:
    LowFree: 低位可以達到高位記憶體一樣的作用，而且它還能夠被核心用來記錄一些自己的資料結構。
                   Among many other things, it is where everything from the Slab is
                   allocated.  Bad things happen when you're out of lowmem.

    SwapTotal: 交換空間的總和

    SwapFree: 從RAM中被替換出暫時存在磁碟上的空間大小

    Dirty: 等待被寫回到磁碟的記憶體大小。

    Writeback: 正在被寫回到磁碟的記憶體大小。

    Mapped: 影射檔案的大小。

    Slab: 核心資料結構快取

    VmallocTotal: vmalloc記憶體大小

    VmallocUsed: 已經被使用的虛擬記憶體大小。

    VmallocChunk: largest contigious block of vmalloc area which is free

    CommitLimit: Based on the overcommit ratio('vm.overcommit_ratio'),
              this is the total amount of  memory currently available to
              be allocated on the system. This limit is only adhered to
              if strict overcommit accounting is enabled (mode 2 in
              'vm.overcommit_memory').
              The CommitLimit is calculated with the following formula:
              CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
              For example, on a system with 1G of physical RAM and 7G
              of swap with a `vm.overcommit_ratio` of 30 it would
              yield a CommitLimit of 7.3G.
              For more details, see the memory overcommit documentation
              in vm/overcommit-accounting.
            
Committed_AS: The amount of memory presently allocated on
the system.
The committed memory is a sum of all of the memory which
              has been allocated by processes, even if it has not been
              "used" by them as of yet. A process which malloc()'s 1G
              of memory, but only touches 300M of it will only show up
              as using 300M of memory even if it has the address space
              allocated for the entire 1G. This 1G is memory which has
              been "committed" to by the VM and can be used at any time
              by the allocating application. With strict overcommit
              enabled on the system (mode 2 in 'vm.overcommit_memory'),
              allocations which would exceed the CommitLimit (detailed
              above) will not be permitted. This is useful if one needs
              to guarantee that processes will not fail due to lack of
              memory once that memory has been successfully allocated.

    VmallocTotal: 可以vmalloc虛擬記憶體大小

    VmallocUsed: 已經被使用的虛擬記憶體大小。

    VmallocChunk: largest contigious block of vmalloc area which is free

提示：

使用adb shell cat /proc/meminfo 命令，檢視剩餘的空間還有多少，通常的系統剩餘空間是: MemFree + cached

top

top命令是Linux下常用的效能分析工具，能夠實時顯示系統中各個程式的資源佔用狀況，類似於Windows的工作管理員。下面詳細介紹它的使用方法。