Filesystem Cache

Linux does extensively use free memory to cache filesystem pages.

Drop Caches

Since linux-2.6.16 there is a mechanism to explicitly drop the filesystem cache. This can be achieved simply by echoing a number to the file /proc/sys/vm/drop_caches. Valid numbers are:

Number	Effect
1	drop page cache
2	drop dentries and inodes
3	combination of 1 and 2