具可調整品質保證的高效率即時硬碟排程架構

• Main Authors: Cheng-Han Tsai, 蔡承翰
• Other Authors: Tai-Yi Huang
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/60779597887804910666

博士 === 國立清華大學 === 資訊工程學系 === 96 === A multimedia server requires a real-time disk-scheduling algorithm to deliver isochronous data for real-time streams. Traditional disk-scheduling algorithms focus on providing good quality in a best-effort manner. In this paper, we propose a novel real-time disk-scheduling algorithm called WRR-SCAN (Weighted-Round-Robin-SCAN) to provide quality guarantees for all in-service streams encoded at variable bit rates and bounded response times for aperiodic jobs. WRR-SCAN divides a real-time stream into guaranteed jobs and optional jobs. The admission control admits a stream as long as its guaranteed jobs are satisfied. Such a decision is made in O(1) time as WRR-SCAN reserves a fixed weight for each stream. WRR-SCAN incorporates an aggressive policy to dynamically reclaim unused bandwidth during run-time. The reclaimed bandwidth is used to serve optional jobs or more aperiodic jobs. We conducted a set of simulations to compare WRR-SCAN with a set of referred disk-scheduling algorithms. The evaluations are conducted on a commonly-used disk simulator with traces from a real multimedia server. The experimental results show that WRR-SCAN provides significantly better quality for real-time streams and yields considerably shorter response times for aperiodic jobs.