Idle process

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The so-called idle process (. English system idle process ) is a "pseudo" - process , which as a clipboard for "free" or unused processor time can be understood. Processor unused time represents the capacity that is not used by applications . In many operating systems, the idle process is allocated a proportion of processor time when processes are terminated. In return, the idle process is subtracted from processor time if another process needs it or a new process is started.

The idle process is also credited with processor time if no processes are available for execution, because they are e.g. B. to E / A (engl. Operations I / O Operations ) wait. In this way, the process scheduler can be simplified, since this case does not have to be dealt with separately, but simply the idle process is scheduled.

Nowadays, when switching to the idle process, instructions are usually associated with which the CPU is put into a power-saving mode or clocked down, e.g. As the HLT command (short for "halt") on x86 - processors .

In the Windows operating system , the idle process is always displayed in the task manager in the "Processes" tab and often apparently requires a lot of processor power. This is the unused computing time. The sum of the shares of all running processes in the processor utilization (including the idle process) is always 100%. In the "System performance" tab , however, only the CPU performance used by other processes is displayed; the "load" due to the idle process is not included in the total because it does not take up any processor time itself.

On Unix-like operating systems , the command line program top is usually installed, which outputs a value marked with id (for idle task , see above ) in the third line for the percentage of the idle process in the total workload of all processors in the system.

Individual evidence

  1. Ralf Guido Herrtwich, Günter Hommel: Concurrent programs . Springer publishing house. 2nd edition 1994. p. 72.
  2. Andrew S. Tanenbaum: Modern Operating Systems . Person studying. 3rd edition. P. 195.
  3. Martin Grotegut: Windows 7 . Springer Verlag 2011. p. 98.