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Multilevel Feedback Queue

Last update:6/8/2012 3:41:00 AM

Owner and writer:Fatih KABAKCI

The purpose of this project is to examine programming the system of Multilevel Feedback Queue that are used in Cpu scheduling algorithms.This project is made in Java Applet technology.


One of main tasks of Operating Systems is providing service to handle processes in a fair manner.So it tries to use Cpu the most efficient manner as using several algorithms during the service.FCFS(First Come First Served),RR(Round Robin),SJF(Shortest Job First) and some of many Priority algorithms are used by Cpu dispatcher.During Cpu scheduling algorithms are used,processes wait to pass from ready state to running state according related types in different queues.at this point,Processes that is get in Cpu start to serve according different criterias and using as mentioned algorithms above.

As shown above,Cpu scheduling algorithms that are used in more than one queue are used Multilevel Feedback Queue systems.


Three different queue model is performed in this project as shown above.The first two tail,respectively performs Round Robin quantum 20 and Round Robin quantum 10 algorithms.The last tail performs First Come First Serve algorithm.

The processes that have specific burst length and come system at the different times enter Round Robin quantum 20 queue have the highest priority.if job of a process is not complete at specified time interval,it enters the second queue(RR q=10).if there is not any process in the first queue,processes in the second queue are performed.if also job of a process is not complete at specified time interval in this queue,related processes enter the third queue.Processes in third queue wait complete of processes in the first two queue.Starvation which could be trouble can be prevent with aging method in a time shared system.if a process was not taken a milisecond time interval in cpu,it will can be passed more higher priority queue with increasing its priority.As mentioned previously,Operating System runs to provide service processes in a fair manner.


3 queues are used in this project.Processes come to access the first queue in different time interval.The first queue uses Round Robin quantum 20.Processes have between 1 and 40 burst length.As mentioned previously if a process job is not finish in the first queue,it passes the second queue and waits the first queue will clean.if the processes complete in the first queue,the system runs in the second queue.It must be waited the second queue to run in the third queue in the same manner.

if the process in third or second queue waits about 20 milisecond,its priority increases and it is added in a higher priority queue.

The waiting time,turnaround time,response time of each process and cpu utilization are calculated in the program.

Process are summarized below :
  • The process is generated in the different time intervals and added in the first queue.
  • if A process is not complete in the first queue,it is passed the second queue
  • if All of process are finish in the first queue,the processes in second queue run
  • if all of process are finish in the first and second queue,the process in third queue run
  • The processes in third queue are run respectively as they come respectively and they leave
  • it is pretended Starvation problem by using aging method


You can go application file here

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