HOWTO: Partially free RAM memory

1) Flush file system buffers

    sync

2) Free page cache

    echo 1 > /proc/sys/vm/drop_caches

3) Free dentries and inodes

    echo 2 > /proc/sys/vm/drop_caches

4) Free page cache, dentries, inodes

    echo 3 > /proc/sys/vm/drop_caches