linux 下释放cache、swap

当在Linux下频繁存取文件后，物理内存会很快被用光 ……

出于某种考虑，想手工释放cache、swap，可以手工执行如下操作（尽量少用比较好，呵呵……）

cache释放：

/proc/sys/vm/drop_caches (since Linux 2.6.16)

Writing to this file causes the kernel to drop clean caches,dentries and inodes from memory, causing that memory to become free.

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

虚拟内存的释放一般都是伴随着关闭应用程式来说的

可以通过命令刷新swap还原到初始状态：

swapoff -a

swapon -a

例如：

[root@wjlcn1026 vm]# free -m

             total       used       free     shared    buffers     cached

Mem:          1744        913        830          0          0        491

-/+ buffers/cache:        422       1321

Swap:         2015       1097        918

[root@wjlcn1026 vm]# swapoff -a

[root@wjlcn1026 vm]# free -m

             total       used       free     shared    buffers     cached

Mem:          1744       1109        634          0          5        694

-/+ buffers/cache:        410       1333

Swap:            0          0          0

[root@wjlcn1026 vm]# swapon -a

[root@wjlcn1026 vm]# free -m

             total       used       free     shared    buffers     cached

Mem:          1744       1116        627          0          5        694

-/+ buffers/cache:        417       1326

Swap:         2015          0       2015