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What is SJF scheduling example?

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What is SJF scheduling example?

Example. In the following example, there are five jobs named as P1, P2, P3, P4 and P5. Their arrival time and burst time are given in the table below. Since, No Process arrives at time 0 hence; there will be an empty slot in the Gantt chart from time 0 to 1 (the time at which the first process arrives).

What is FCFS and SJF?

First Come First Served (FCFS) Shortest Job First (SJF) First Come First Served (FCFS) executes the processes in the order in which they arrive i.e. the process that arrives first is executed first. Shortest Job First (SJF) executes the processes based upon their burst time i.e. in ascending order of their burst times.

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How is SJF scheduling calculated?

Waiting Time =Total waiting Time – No. of Milisec. Process executed – Arrival Time P1 = 20 – 1 – 0 = 19 ms, P2 = 4 – 3 – 1 = 0 ms, P3 = 8 – 0 – 2 = 6ms P4 = 13 – 0 – 3 = 10 ms, P5 = 5 – 0 – 4 = 1 ms. Total Waiting Time = 36 mills.

Which data structure is used in SJF?

Shortest job first algorithm is implemented through min heap data structure.

Why is SJF or SRTF scheduling difficult to implement in a real OS?

Shortest Job First Scheduling Characteristics  The real difficulty with the SJF algorithm is, to know the length of the next CPU request.  SJF minimizes the average waiting time[3] because it services small processes before it services large ones.

What are the advantages and disadvantages of SJF scheduling?

2. Shortest Job First (SJF) [Preemptive and Non- Prememptive]:

  • Advantages – Shortest jobs are favored. It is provably optimal, in that it gives the minimum average waiting time for a given set of processes.
  • Disadvantages – SJF may cause starvation, if shorter processes keep coming. This problem is solved by aging.
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What is the full form of SJF?

Shortest job next (SJN), also known as shortest job first (SJF) or shortest process next (SPN), is a scheduling policy that selects for execution the waiting process with the smallest execution time.

What is non-preemptive SJF?

Shortest job first (SJF) or shortest job next, is a scheduling policy that selects the waiting process with the smallest execution time to execute next. SJN is a non-preemptive algorithm. Shortest Job first has the advantage of having a minimum average waiting time among all scheduling algorithms.

How does SJF calculate throughput?

Wait time – Average time a process spends in the run queue. Throughput – Number of processes completed / time unit….

Metric SJF
Waiting (0+4+CS+9+2CS+17+3CS)/4 = 7.5 ignoring CS
Throughput 4/(26 + 3CS)
Response (0+4+CS+9+2CS+17+3CS)/4 = 7.5 ignoring CS

How does SJF calculate waiting time?

4.2 Shortest-Job-First (SJF) Scheduling The average waiting time is ( 3 + 16 + 9 + 0 ) / 4 = 7.0 ms. If we were using the FCFS scheduling, then the average waiting time would be 10.25 ms. SJF is optimal in that it gives the minimum average waiting time for a given set of processes.

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How is preemptive calculated SJF?

P2 has 4ms , so as P2 is shorter, P1 is preempted and P2 process starts executing. At ( t = 2ms ), P3 process has arrived. At this time, P1(remaining time) = 5ms, P2(remaining time ) = 3 ms , P3 = 2ms….SJF Preemptive Example.

Process Arrival time Burst Time
P1 0 6
P2 1 4
P3 2 2
P4 3 3

Can SJF scheduling be considered as priority scheduling justify?

Priority scheduling is a more general case of SJF, in which each job is assigned a priority and the job with the highest priority gets scheduled first….5.3. 3 Priority Scheduling.

Process Burst Time Priority
P2 1 1
P3 2 4
P4 1 5
P5 5 2