So your hacking away on your linux box when suddenly you notice that you only have 200MB out of 32GB available RAM, you freak out and pull out your hair as you don’t know what could possibly be using so much RAM. Don’t panic, this is normal your box just has most of the memory cached. It doesn’t pose any danger as your system will free it up automatically as you need it. In case you need it here is how to free up all of the cached memory.
free && sync && echo 3 > /proc/sys/vm/drop_caches && free