Why Linux Consumes Available Memory?

You may be aware of Linux high Memory consumption, while searching details I found two articles very well explaining high memory consumption, here I am sharing for your reference.

Article 1
Linux is borrowing unused memory for disk caching.Disk caching makes the system much faster.If your applications want more memory, they just take back a chunk that the disk cache borrowed. Disk cache can always be given back to applications immediately! You are not low on ram!

Article 2
Linux uses all available memory to do I/O cache – that is to save portions of the hard disk space and to serve it straight from the memory avoiding relatively long disk access. This is why for instance when you copy several large files from one place to another several times in a row, second copy takes significantly fewer time then the first. This is also the reason why, in Linux, it takes a second to write a megabyte to a floppy disk, a device known for its slowliness – the data being written to the memory and not to an actual disk.

Also, disks optimized to read and write large chunks of data. Average program on the contrary reads and writes small chunks of data. To speed up the process, Linux collects several small read and write requests into bigger thus increasing disk performance. This however requires memory.

What many people don’t realize is that Linux uses all available memory and always tries to free even more memory for caching. When it sees a piece of memory that some program did claim, but doesn’t use very often, it will copy it to swap partition and use the actual memory for caching. Once the program will try to do something with this memory piece, Linux will detect this and read the contents of the memory piece from swap partition back to the real RAM.

The real issue here is that this mechanism should be very balanced. Linux is optimized to use all available memory for caching. When it doesn’t have enough memory, time it takes to access data on disks will rise! Since all programs leak memory, over the time Linux will have less and less memory for caching and disk access speed will drop.

How do I find actual free ram?

free -m
             total       used       free     shared    buffers     cached
Mem:          2017       1964         53          0        190       1515
-/+ buffers/cache:        257       1760
Swap:          502          1        500

Here actual free RAM is 1760
Hope above may be useful for newbie or may be experienced Linux admins for explanation.