Multithread Affinity Scheduling Using a Decision Maker

Abstract

In a multiprocessor-multithread Operating System (OS), scheduling has two dimensions. The operating system has to decide which thread to run and which Central Processing Unit (CPU) to run it on. Assume the threads are independent and each thread has a priority, the operating system selects a thread with the highest priority and assigns it to the first free CPU. Usually, each CPU has its private cache. To increase the throughput of the system, it is preferred to use affinity scheduling. The affinity scheduling concept is to make an effort to have a thread run on the same CPU it ran on the last time. The existing affinity scheduling is implemented by using a two-level scheduling algorithm. In this paper a new approach is designed to implement independent multithread scheduling on a multiprocessor system. The design approach uses a decision maker to compute a new priority for each ready thread according to the thread pre-priority and affinity. The results show that by using the new priority, the goal of having affinity is satisfied in addition to taking the pre-priority of the thread in consideration. Also, the design approach reduces the scheduling time because it implements affinity scheduling and priority scheduling by employing a one level scheduling algorithm.