I have VPS with 2GB of RAM running Ubuntu. There are three sites using database on this server - two on WordPress and one on custom script. All of them get max few hits per day.
MySQL always had pretty high RAM usage - usually something around 25%. It's not that much but it looked weird compared to other processes using 1% or 2%.
Today I upgraded OS to Ubuntu 16.04 and now MySQL uses even more RAM - currently it's stuck at 42%.
My question is: is it normal? There are lot of posts about minimizing memory usage by MySQL but I don't know if it's necessary. After all half of RAM is still empty.