Creating Thread-to-Core and Task-to-Thread Affinity

When developing parallel applications with the Threading Building Blocks library, we create tasks by using the high-level execution interfaces or the low-level APIs. These tasks are scheduled by the TBB library onto software threads using work stealing. These software threads are scheduled by the Operating System (OS) onto the platform’s cores (hardware threads). In this chapter, we discuss the features in TBB that let us influence the scheduling choices made by the OS and by TBB. Thread-to-core affinity is used when we want to influence the OS so that it schedules the software threads onto particular core(s). Task-to-thread affinity is used when we want to influence the TBB scheduler so that it schedules tasks onto particular software threads. Depending on what we are trying to achieve, we may be interested in one kind of affinity or the other, or a combination of both.