How to clear cached memory on linux

Since 2.6.16 you need only echo to clear cached memory on Linux box.

This will clear all cached memory.

echo 3 > /proc/sys/vm/drop_caches

You can clear only part of it by using 1 or 2. All options:

• 1 to clear cached pages.
• 2 to clear dentries and inodes. 
• 3 to clear all cached memory.

Links:
I found this advise here
Some notes about Linux VFS
Linux Page cache