一种新颖的带模糊截止时限的磁盘调度算法

A Novel Disk Scheduling Algorithm with Fuzzy Deadlines

设计了一种新的基于截止时限的磁盘调度算法,该算法支持带多优先级的请求。对于某些实时要求,其截止时限是不确定的或者不精确的,该算法采用模糊集来描述这类不确定性,模糊截止时限的隶属度函数表示对请求完成时间的满意程度。调度的目的是最优的指定优先级,使得截止时限的满意程度最大化。根据请求截止时限的不同,把满意程度划分为若干连续的区间。在每个不同的区间内,每个请求都对应有修正的截止时限,把请求按照其修正的截止时限非减的顺序分配优先级,才能实现请求优先级的最优配置。仿真结果表明该算法能有效的分配请求的优先级,降低请求的丢失率,保证了更多的请求得到满足。

A new deadline driven disk scheduling algorithm is designed for multimedia servers. The proposed algorithm supports the requests with multi - priority. For some real time requests, their deadlines are not deterministic and accurate. The proposed algorithm describes this kind of uncertainty with fuzzy set. The member functions of fuzzy deadlines denote grade of satisfaction with respect to completion time of requests. The goal of scheduling is to find an optimal assignment of priorities such that the satisfaction associated with deadline is maximized. Grade of satisfaction are partitioned into some continuous intervals according to deadlines of requests. There are corresponding modified deadline for every request in any interval. The optimal priority allocation of requests can be obtained by scheduling requests according to their modified deadlines. Result of simulation shows that the algorithm can assign efficiently the priority to requests.