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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.
Idle is a state that a computer processor is in when it is not being used by any program. Every program or task that runs on a computer system occupies a certain amount of processing time on the CPU. If the CPU has completed all tasks it is idle. Modern processors use idle time to save power.
The dynamic power (switching power) dissipated by a chip is C·V 2 ·A·f, where C is the capacitance being switched per clock cycle, V is voltage, A is the activity factor [1] indicating the average number of switching events per clock cycle by the transistors in the chip (as a unitless quantity) and f is the clock frequency.
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.
The short-term scheduler (also known as the CPU scheduler) decides which of the ready, in-memory processes is to be executed (allocated a CPU) after a clock interrupt, an I/O interrupt, an operating system call or another form of signal. Thus the short-term scheduler makes scheduling decisions much more frequently than the long-term or mid-term ...
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.
Finally, tasks required of modern computers often emphasize quite different components, so that resolving a bottleneck for one task may not affect the performance of another. For these reasons, upgrading a CPU does not always have a dramatic effect. The concept of being CPU-bound is now one of many factors considered in modern computing ...