System Monitor is very useful Gnome Shell extension for displaying system information on top-panel, such as memory usage, cpu usage, network rates.
To Install System Monitor Applet in Gnome Shell (Ubuntu/Fedora) just enter the following commands in the Terminal:
Install the dependencies with the following command:
1. Now, install git to get the source.
Create a folder for git projects and git clone the source:
2. Create directory of gnome shell extensions and make a link.
3. Install the schema:
4. Install the configurator:
5. Now, restart gnome-shell by Alt+F2 and type 'r' and Press Enter (or log-out and log-in back). Go to Advance Settings to enable this extension. If you don't have Gnome Tweak Tool, Install it from here.
Here is the System Monitor Applet Page on GitHub