Energy Efficient Real-Time Co-Scheduling of Multimedia DSP Jobs

一方面為了節省成本，一方面為了滿足多媒體應用的需求，DSP 現已廣泛被使用於嵌入式系統之中。然而，DSP 上即時工作省電排程的相關研究為數不多。針對一個 DSP 上的週期性工作，像是 H.264 的解壓縮工作，本篇論文提出了一組基於滑動視窗的線上排程演算法，產生一序列的排程時間點與相對應的處理器速度。演算法的效果經由實作與模擬兩種方式作為評估，最多可達到 45% 的能源節省，而線上預測執行時間造成時限超出的情形最多亦不會超過 4%。While DSP's are now widely adopted in many embedded systems in the cost minimization and the resolving of computing needs of various multimedia applications, little work is done for energy-efficient real-time job scheduling over DSP's. As motivated by the needs, a set of sliding-window-based algorithms are proposed. A sequence of time points and their corresponding processor speeds is generated to run jobs of a periodic task on the DSP, such as that for the decoding of an H.264 stream. An online competitive DVS scheme for energy minimization with constrained buffer size consideration is proposed, and the capability of the scheme is evaluated by a series of experiments over real and synthesized traces. It was shown that roughly 45% energy saving was possible for many cases, and prediction errors were not significant enough to result in more than 4% in deadline missing.1 Introduction 1 2 Problem Formation 4 2.1 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Problem Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 Voltage-Scaling Algorithms for Speed Schedules 8 3.1 Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.1 An ECMASP Solution - SW-ASP . . . . . . . . . . . . . . . . . 8 3.1.2 An ECMRSP Solution - SW-RSP . . . . . . . . . . . . . . . . . 12 3.2 Lower Bounds and Competitive Ratios . . . . . . . . . . . . . . . . . . . 15 3.3 The Buffer Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4 Experiments 22 4.1 Environment Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.2 Simulation Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4.3 Experimental Results - A Case Study . . . . . . . . . . . . . . . . . . . . 27 5 Conclusion and FutureWork 31 Bibliography 3