linux內存和swap

# sync && echo 3 >/proc/sys/vm/drop_caches && sleep 2 && echo 0 >/proc/sys/vm/drop_caches

free -m

各參數含義：

   1:  total：總物理內存

   2:  used：已使用內存

   3:  free：完全未被使用的內存

   4:  shared：應用程序共享內存

   5:  buffers：緩存，主要用於目錄方面,inode值等

   6:  cached：緩存，用於已打開的文件

   7:  -buffers/cache：應用程序使用的內存大小，used減去緩存值

   8:  +buffers/cache：所有可供應用程序使用的內存大小，free加上緩存值

   9:  其中：

  10:  total = used + free

  11:  -buffers/cache=used-buffers-cached，應用程序真實使用的內存大小

  12:  +buffers/cache=free+buffers+cached，服務器真實還可利用的內存大小 

 

Writing to this file causes the kernel to drop clean caches,dentries and inodes from memory, causing that memory to becomefree.
To free pagecache, use echo 1 > /proc/sys/vm/drop_caches;
to free dentries and inodes, use echo 2 > /proc/sys/vm/drop_caches;
to free pagecache, dentries and inodes, use echo 3 >/proc/sys/vm/drop_caches.
Because this is a non-destructive operation and dirty objects are not freeable, the user should run sync first.

轉自 http://www.linuxidc.com/Linux/2012-04/58184.htm