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Operating Systems | Scheduling Algorithms: HRRN

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Highest Response Ratio Next(HRRN) Response ration of a process in ready state at a moment is the ratio of sum of service time (equal to burst time) required and waiting time till that moment to the burst time. Among available processes on ready state ,a process with highest response ratio get allocated to CPU by a scheduler with HRRN algorithm. If response ratios are equal next priority will for one which is arrived first and even that also similar then next is for onw with lowest process ID. Example: Calculate completion time, turn around time and waiting time for the following processes using non-preemptive HRRN algorithm? Process AT BT P1 0 4 P2 1 3 P3 1 1 P4 3 2 Answer: The sequences of allocation of process into CPU can be depicted as follows: TAT = CT - AT & WT = TAT - BT ...
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Operating Systems | Scheduling Algorithms : Round Robin

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Round Robin Features : Most popular algorithm of all Practically implementable Implementable with basic data structures like queue Extremely lesser starvation Optimum efficiency can be set by controlling time quantum The round robin algorithm will continuously switch between processes if a process in CPU (under execution) exceeds a time limit set by OS called time quantum . Flow Chart : Scheduler allocated process to for execution. CPU starts monitoring the execution time right after from allocation. If the process completes its execution before exceeding time quantum, OS forwards the process to termination state. else, the processes gets preempted once the time quantum limit exceeded and if the process finished at this moment, OS moves the process to termination state, else it moves to ready queue and iterates over the whole process listed above. Example : Consider the following table of processes and calculate completion time, turn around time and waiting tim...
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Operating Systems | Time Aspects of Process

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Important time parameters of process Arrival Time(AT) Entry time of process into ready queue. Burst Time(BT) Amount time spend for execution of process in CPU. Completion Time(CT) Finishing time of execution of the process Waiting Time(WT) Amount of time spend by process for waiting CPU after arrival and before completion. Turn Around Time(TAT) Time gap between arrival and completion time of a process. Response Time(RT) The range of time between initial scheduling and entry/arrival time of process. I/O Time The time spend for completion of input output request. For an preemptive algorithm the the waiting time and burst time may be intermittent time slices(BT1/ WT1,BT2/ WT2...) of its over all burst time(BT)/waiting time(WT). RT = tX - AT CT - AT = BT + WT WT = TAT - BT | Previous | Next | Home |
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