linux内存和swap

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

free -m

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各参数含义：

1:  total：总物理内存

2:  used：已使用内存

3:  free：完全未被使用的内存

4:  shared：应用程序共享内存

5:  buffers：缓存，主要用于目录方面,inode值等

6:  cached：缓存，用于已打开的文件

7:  -buffers/cache：应用程序使用的内存大小，used减去缓存值

8:  +buffers/cache：所有可供应用程序使用的内存大小，free加上缓存值

9:  其中：

10:  total = used + free

11:  -buffers/cache=used-buffers-cached，应用程序真实使用的内存大小

12:  +buffers/cache=free+buffers+cached，服务器真实还可利用的内存大小

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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.

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