Processor affinity
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- Snippet from Wikipedia: Processor affinity
In computer science, processor affinity, also called CPU pinning or cache affinity, enables the binding and unbinding of a process or a thread to a central processing unit (CPU) or a range of CPUs, so that the process or thread will execute only on the designated CPU or CPUs rather than any CPU. This can be viewed as a modification of the native central queue scheduling algorithm in a symmetric multiprocessing operating system. Each item in the queue has a tag indicating its kin processor. At the time of resource allocation, each task is allocated to its kin processor in preference to others.
Scheduling-algorithm implementations vary in adherence to processor affinity. Under certain circumstances, some implementations will allow a task to change to another processor if it results in higher efficiency. For example, when two processor-intensive tasks (A and B) have affinity to one processor while another processor remains unused, many schedulers will shift task B to the second processor in order to maximize processor use. Task B will then acquire affinity with the second processor, while task A will continue to have affinity with the original processor.
On most operating systems, the set of processors a process or thread is allowed (or preferred) to run on is expressed as an affinity mask, which is a bit mask corresponding to the system's cores.