Where does the memory go?

Question

ubuntu

Installed munin, and as usual, great knowledge increases sadness :) The
question is simple - where does the server's memory go or what is it spent on?
Attached are 2 charts.
Only 4 gigabytes of RAM.
swap zero
The dip and the rising chart is the moment of reloading.
LA is almost half a percent or less, basically the server pulls 5 sites, while 200-300 uniques per day the
first file is small in size, the second is 3000 * 3000 pixels


Added today at 14-45 Moscow time
as it frighteningly eats up a lot of memory ...

Answer 1

The file cache eats up your memory. This is normal for web servers.

Answer 2

normal situation for a webserver. there is no swap. all right