System Idle Process

The system idle process is a process which runs on the computer when the CPU has nothing to do. Technically speaking, the system idle process is a software which runs when the computer system has no task to perform.

System Idle Process - What Is It?

The kernel threads of system idle process run, when there is no other thread scheduled on a particular CPU. In the windows task manager, one can see different column names such as 'Image Name', 'CPU', 'Memory Usage', etc. In the CPU column, one can generally see values ranging in the 90s against 'System Idle Process' of 'Image Name' column. These values indicate that most of the CPU resources are not used at all. In simple language, the CPU is waiting to do some work and has around 90% of unused resources. This percentage which stays near 90% during the idle phase, shoots up when one starts performing different functions on the computer.

The purpose of incorporating 'system idle process' is to eliminate 'special case' from the scheduler. Let us say for example, that idle threads are not present in the system. In this case, a condition could arise in which, even a single thread isn't running. It is definitely an 'exception'; it is thus, dealt with by having the 'idle thread' running. To find out the CPU usage during a system idle process, one should open the windows task manager. It is done by pressing the following combination of keys: Ctrl+Del+Alt.

One of the important functions of this process is power saving. In Windows 2000 and later versions, threads are employed by the system idle process in saving power. The process of power saving can be understood properly by obtaining information about the firmware and hardware capabilities of the system being used. The following example would help in better understanding of the power saving concept. Idle thread on x86 processors (Windows 2000) run the HLT instructions in a loop. The HLT instructions are used in turning off many internal components. These internal components start functioning only after an interrupt request is encountered.

Windows NT
Understanding the Windows NT operating system provides us with an idea about the system idle process, and also the functions underlying it. The Windows NT operating system carries out multi-tasking by means of a concept called multi-threading. The different operations performed with the help of threads on Windows NT operating systems are prioritized. The activity of giving priority to a particular task helps in carrying out more important tasks before it. The less important ones on the other hand are completed after it.

The computer chip is capable of performing just one task at a time. However, the multi-threading functionality enables it to switch between threads and thereby perform multiple functions. The NT scheduler is used in the task of switching between threads. Different algorithms are employed for the functioning of NT schedulers.

With the information about system idle process presented above, you must have had a fair idea about the same. The value of 90-100% displayed by the task manager shouldn't be confused with the CPU usage of the computer. In fact, it presents information about the CPU resources that are unused. The information provided above, should thus, prove to be helpful.