Simple monitor extension for GNOME. Shows a widget on the top panel with the percentage of CPU and memory used. If clicked, shows the ten most cpu-intensive processes and the ten most memory-consuming processes.
To install, clone repository and copy it in ~/.local/share/gnome-shell/extensions/simple-monitor@fcaballerop.github.io
After doing so, restart the GNOME shell by doing Alt+F2 and inserting 'r' in the prompt. It will then be available in the 'Extensions' configuration screen.