(转)Linux下清理Cache方法

频繁的文件访问会导致系统的Cache使用量大增, 系统运行缓慢。

1 首先用free 命令查看内存的使用：
$ free -m
             total       used       free     shared    buffers     cached
Mem:   3955       3926         28          0         55            3459

2 运行sync将dirty的内容写回硬盘
$sync
3 通过修改proc系统的drop_caches清理free的cache
$echo 3 > /proc/sys/vm/drop_caches

关于drop_caches的详细文档如下：
Writing to this will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free.
To free pagecache:
    * echo 1 > /proc/sys/vm/drop_caches
To free dentries and inodes:
    * echo 2 > /proc/sys/vm/drop_caches
To free pagecache, dentries and inodes:
    * echo 3 > /proc/sys/vm/drop_caches
As this is a non-destructive operation, and dirty objects are not freeable, the user should run "sync" first in order to make sure all cached objects are freed.

参考文献：

[1] 转载地址：

http://blog.chinaunix.net/uid-25505925-id-180921.html

http://m.blog.csdn.net/article/details?id=4336075.