The first great thing about htop is that it will show you your usage per CPU, as well as a meaningful text graph of your memory and swap usage right at the top. I find this much easier to understand at a glance than the default output from top.
Installing htop on Ubuntu
Installing on Ubuntu is as simple as apt-getâ€¦ You can also grab the source from the htop site linked at the bottom of this article.
sudo apt-get install htop
Once installed, just type htop at a terminal to launch it, and notice the great text-mode graph at the top of the display: