cpuanddiskschedulingalgorithms-在線瀏覽
2024-12-02 21:50本頁面
【正文】 han the expiration time the scheduler takes the item from the queue. Anticipatory I/O Scheduler ? This algorithm works with the Deadline algorithm. ? This algorithm causes a 6 m/s delay after a read request. ? It does this assuming that the next read request may e from the same section on the disk. If so then the operation is processed immediately. ? If not it moves on Earliest Deadline First ? Used in Real Time Operating Systems ? Household Appliances ? Industrial Robots ? Spacecraft ? Programmable Thermostats ? Quite simply, when a process is finished the queue is searched for a process with the next closest deadline. ? This method works only if the CPU is not at 100%. ? If it is then the results are unpredictable. ? Each job is characterized by the following: ? Arrival time ? Execution requirements ? Deadline 。 one level, and placed at the end of the nexthighest queue. This allows I/O bound processes to be favored by the scheduler and allows processes to 39。CPU and Disk Scheduling Algorithms By: Stefan Peterson Lets Start with Windows ? In the Beginning ? DOS and prior to ? Windows did not multitask and thus had no need for CPU scheduling ? Windows ? Used a nonpreemptive scheduler Non Preemptive Scheduling ? Programs do not get interrupted ? Relies on cooperative multitasking ? The OS relied on the program to tell it when it was finished. Windows 95 and After ? Up until Vista Windows used a multilevel feedback queue. ? 32 levels defined from 0 – 31 ? 0 belonging to Windows ? 1 – 15 are normal priorities ? 16 – 31 are for soft real time priorities ? These
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