Monitoring System Usage with systat

  An overburdened CPU is another obvious place to look for performance problems
on your system. Similarly io can be a bottleneck in proper system performance. You can watch various parameters if you install sysstat package.
On Ubuntu you can install with

  $ sudo apt-get install sysstat
 
 The sysstat package contains the following system performance tools:
  * sar - collects and reports system activity information;
  * iostat - reports CPU utilization and I/O statistics for disks;
  * mpstat - reports global and per-processor statistics;
  * pidstat - reports statistics for Linux tasks (processes);
  * sadf - displays data collected by sar in various formats.
 

       
See the screen shot of iostat command run from a terminal.
 Iostat can display cpu  usage statistics. The following command prints cpu stats every 3 sec

$ iostat -c 3 

To Print time stamp with CPU report you can use

$ iostat -c -t

 You can use pidstat to display detailed information on processes. See the screen shot below.