The Activity Monitor is quite useful for pulling up the CPU, System Memory, and Network activity as well as Disk Activity and Disk Usage. The dock icon can be a useful tool all on its own, without having to keep the Activity Monitor window up and running. You can view CPU History as well as CPU, Disk, Memory, or Network Usage.
1. Open Finder and go to your Applications directory. In the Utilities directory, open Activity Monitor.
2. Right-click (Ctrl+click) the dock icon and select Keep in Dock.
3. Close the Activity Monitor window.
4. Right-click (Ctrl+click) the dock icon. Use the context menu and mouseover Dock Icon.
5. Select one of the following options:
Show CPU Usage
Show CPU History
Show Network Usage
Show Disk Activity
Show Memory Usage
You can keep an eye on the monitored activity while working on other tasks. When you want to stop displaying activity on the dock icon, right-click (Ctrl+click) the dock icon, mouse over Dock Icon and select Show Application Icon.