A Study on the Scheduling Algorithm for Real Time Context Switching
Date Issued
2006
Date
2006
Author(s)
Lin, Tse-Hsun
DOI
zh-TW
Abstract
With the growth of the demand for real time multimedia services (such as video streaming, and VoIP, etc), providing high quality real time services becomes an issue. Among the many factors affecting the performance, the connection speed and the efficiency of the CPU scheduling algorithm are the main factors. In the past CPU scheduling algorithms, they usually focus on how to fairly allocate or reserve resources for different processes, or arrange the processing sequence based on these processes priority. Among these scheduling algorithms, they usually do not consider the effect of the Context-Switch on the CPU efficiency, that is, the expending time on memory movement and the process information storage. In fact, frequent Context-Switching may lead to high overhead, and lengthen the computing time of processes. Further more, it may affect the quality of real time processes, for example, leading to larger delay, jitter, dropping ratio, etc.
In this thesis, we consider the effect of Context-Switch on CPU efficiency and propose two CPU scheduling algorithms, called “Context-Switch Overhead aware” and “Pre-Informed” scheduling algorithm. The design philosophy of Context-Switch Overhead aware scheduling algorithm is to reduce the number of Context-Switch operations, to make the resource usage more efficient, and then increase the quality of real time multimedia applications. When new real time requests arrive, the Pre-Informed scheduling algorithm will allocate required resources to these tasks based on their application types. It will then ensure every real time request has enough computing resource to protect and improve the performance of the multimedia application. The efficiency of these two designs is validated by simulation experiments, and then are compared with Earliest Deadline First (EDF), First Come First Serve (FIFO), and Start-time Fair Queueing (SFQ) scheduling algorithms. In CPU overloaded situation, the Context-Switch Overhead aware scheduling algorithm can raise the effective efficiency of the system, and then promote the quality of the real time application. If the demand of the performance of non real time processes is not high, the quality of the real time multimedia applications of Pre-Informed scheduling algorithm is the best.
Subjects
中央處理器
排程
Context Switch
CPU
Scheduling
Type
thesis
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