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However, the idle process does not use up computer resources (even when stated to be running at a high percent). Its CPU time "usage" is a measure of how much CPU time is not being used by other threads. In Windows 2000 and later the threads in the System Idle Process are also used to implement CPU power saving.
ACPI 1.0 (1996) defines a way for a CPU to go to idle "C states", but defines no frequency-scaling system. ACPI 2.0 (2000) introduces a system of P states (power-performance states) that a processor can use to communicate its possible frequency–power settings to the OS. The operating system then sets the speed as needed by switching between ...
Many operating systems, for example Windows, [1] Linux, [2] and macOS [3] will run an idle task, which is a special task loaded by the OS scheduler on a CPU when there is nothing for the CPU 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.
BITS Download Manager – A download manager for Windows that creates BITS Jobs. [8] BITSync – An open source utility that uses BITS to perform file synchronization on Server Message Block network shares. [9] Civilization V – Uses BITS to download mod packages. Endless OS installer for Windows – Uses BITS to download OS images. [10]
When a program wants to time its own operation, it can use a function like the POSIX clock() function, which returns the CPU time used by the program. POSIX allows this clock to start at an arbitrary value, so to measure elapsed time, a program calls clock(), does some work, then calls clock() again. [1] The difference is the time needed to do ...
In many applications, the CPU and other components are idle much of the time, so idle power contributes significantly to overall system power usage. When the CPU uses power management features to reduce energy use, other components, such as the motherboard and chipset, take up a larger proportion of the computer's energy.
An idle computer has a load number of 0 (the idle process is not counted). Each process using or waiting for CPU (the ready queue or run queue) increments the load number by 1. Each process that terminates decrements it by 1. Most UNIX systems count only processes in the running (on CPU) or runnable (waiting for CPU) states.
As other resources are also shared, processor affinity alone cannot be used as the basis for CPU dispatching. If a process has recently run on one virtual hyper-threaded CPU in a given core, and that virtual CPU is currently busy but its partner CPU is not, cache affinity would suggest that the process should be dispatched to the idle partner CPU.