Here is a way how to clear the linux system buffers. You will need to run this command as root.
To clear the pagecache, dentries and inodes
echo 3 > /proc/sys/vm/drop_caches
To clear just the pagecache, use the following command
echo 1 > /proc/sys/vm/drop_caches
Similarly, to delete just the dentries and inodes :
echo 2 > /proc/sys/vm/drop_caches
This is a non-destructive operation and will only free things that are completely unused.