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.

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