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(Redirected from Idle loop)
In computing, an 'idle task' is a special task loaded by the OS scheduler ''only'' when there is nothing for the computer to do. The idle task can be hard-coded into the scheduler, or it can be implemented as a separate task with the lowest possible priority. An advantage of the latter approach is that programs monitoring the system status can see the idle task along with all other tasks; an example is Windows NT's System idle process.
On modern processors, where a HLT (halt) instruction saves significant amounts of power and heat, the idle task almost always consists of a loop which repeatedly executes HLT instructions. However, on older computers, where temperature dissipation was almost constant with CPU load, the program would often do useless things, like blink the front panel lights in an amusing or recognizable pattern.
Often, this meant that someone in the computer room of a timeshared system could glance at the front panel lights to see how busy the machine was. If the idle pattern only rarely showed, a programmer might go to lunch before running a job but if the idle pattern blinked steadily, the programmer would run the job immediately.
In Unix-like operating systems such as Linux, the idle task has process ID zero, and never exits.
★ HLT
★ System Idle Process
★ X86
★ Computer Architecture
★ Instruction Set
In computing, an 'idle task' is a special task loaded by the OS scheduler ''only'' when there is nothing for the computer to do. The idle task can be hard-coded into the scheduler, or it can be implemented as a separate task with the lowest possible priority. An advantage of the latter approach is that programs monitoring the system status can see the idle task along with all other tasks; an example is Windows NT's System idle process.
On modern processors, where a HLT (halt) instruction saves significant amounts of power and heat, the idle task almost always consists of a loop which repeatedly executes HLT instructions. However, on older computers, where temperature dissipation was almost constant with CPU load, the program would often do useless things, like blink the front panel lights in an amusing or recognizable pattern.
Often, this meant that someone in the computer room of a timeshared system could glance at the front panel lights to see how busy the machine was. If the idle pattern only rarely showed, a programmer might go to lunch before running a job but if the idle pattern blinked steadily, the programmer would run the job immediately.
In Unix-like operating systems such as Linux, the idle task has process ID zero, and never exits.
| Contents |
| See Also |
See Also
★ HLT
★ System Idle Process
★ X86
★ Computer Architecture
★ Instruction Set
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