双头磁盘系统的实时调度算法

Real-Time Disk Scheduling for Two-Headed Disk Systems

对双头磁盘系统模型和调度算法进行实时化扩展，设计了三种实时调度算法：最早截止期优先（ＥＤＦ）算法，可满足的最早截止期优先（Ｆ－ＥＤＦ）算法和忽视超期限请求（ＩＧＭ－ＥＤＦ）算法．由于这三种算法充分考虑了Ｉ／Ｏ请求的截止期限，使双头磁盘系统能满足更多的实时Ｉ／Ｏ请求．实时调度算法的性能模拟实验表明：实时调度算法比非实时算法能更好地满足实时Ｉ／Ｏ请求的期限要求．三种实时调度算法中，ＩＧＭ－ＥＤＦ的性能最好，它很适用于硬实时应用；Ｆ－ＥＤＦ算法的性能次之，它最适合于软实时应用．

A real-time model of the two-headed disk system is presented. Three real-time scheduling algorithms are proposed. They are more suitable than non-real-time in the real-time applications. The simulation experiment shows that real-time algorithms perform better than non-real-time algorithms when serving real-time I/O requests. Among real-time algorithms, IGM-EDF is the best one when employed in the hard real-time environment, and the next one is F-EDF that is useful in soft real-time applications.