StatsDawg

This graph displays percentages of how time on the CPU has been divided among running processes and the operating system. It is currently an aggregate of all the CPUs on the system. Currently 4 states are being tracked. They are:

User

The amount of time that was spent in user mode, which is basically much of the code being run by a particular application that does not require a system call to execute. Most all appliactions run under this mode.

Nice

Like User, the amount of time that was spent in user mode but running at a lower priority than normal. Most background non-essential applications generally fall under this category, although this can be set by the system administrator.

System

The amount of time the CPU was in system or kernel mode. This system switches to this mode anytime a system call is made by the operating system or an application. For instance, accessing the system's disk I/O system must be done using a system call. This allows the operating system to directly manipulate the disk and memory to retrieve or store the data in question. In other words, any time the operating system needs to intervene and do something critial, it will be done so under system mode.

I/O Wait

The amount of time the system is spent waiting for the disk and being unable to do anything further as a result. Note this is not simply the time spent waiting for I/O, say from the system's disk. Rather this is time spent where the operating system could not find anything useful to do that did not depend on waiting for the disk or another I/O system. If the system is spending over 10% of its time in this mode for long durations, it tends to indicate that it is becomming too dependant on usually the disk subsystem, which can have a significant impact on performance.