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On Linux, the CPU affinity of a process can be altered with the taskset(1) program [3] and the sched_setaffinity(2) system call. The affinity of a thread can be altered with one of the library functions: pthread_setaffinity_np(3) or pthread_attr_setaffinity_np(3). On SGI systems, dplace binds a process to a set of CPUs. [4]
An affinity mask is a bit mask indicating what processor(s) a thread or process should be run on by the scheduler of an operating system. [1] Setting the affinity mask for certain processes running under Windows can be useful as there are several system processes (especially on domain controllers) that are restricted to the first CPU / Core.
In Windows NT operating systems, the System Idle Process contains one or more kernel threads which run when no other runnable thread can be scheduled on a CPU. In a multiprocessor system, there is one idle thread associated with each CPU core. For a system with hyperthreading enabled, there is an idle thread for each logical processor.
A task (i.e., a synonym for thread) is the minimal entity that Linux can schedule. However, it can also manage groups of threads, whole multi-threaded processes, and even all the processes of a given user. This design leads to the concept of schedulable entities, where tasks are grouped and managed by the scheduler as a whole.
This switches the threading mode between one thread, two threads or four threads depending on the number of process threads being scheduled at the time. This optimizes the use of the core for minimum response time or maximum throughput. IBM POWER8 has 8 intelligent simultaneous threads per core (SMT8).
A process with two threads of execution, running on one processor Program vs. Process vs. Thread Scheduling, Preemption, Context Switching. In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system. [1]
However, other systems, especially systems implementing so-called M:N threading, use different strategies such as counting the process exactly once for the purpose of load (regardless of the number of threads), or counting only threads currently exposed by the user-thread scheduler to the kernel, which may depend on the level of concurrency set ...
Threads created by the library (via pthread_create) correspond one-to-one with schedulable entities in the kernel (processes, in the Linux case). [4]: 226 This is the simplest of the three threading models (1:1, N:1, and M:N). [4]: 215–216 New threads are created with the clone() system call called through the