[Solved] Trace the sequence of process execution in preemptive SJF scheduling when the following processes arrive: P1(Arrival=0, Burst=8), P2(Arrival=1, Burst=4), P3(Arrival=2, Burst=2).... | Operating Systems

Operating Systems - Shortest Job First (SJF) - Preemptive vs Non-Preemptive

Trace the sequence of process execution in preemptive SJF scheduling when the following processes arrive: P1(Arrival=0, Burst=8), P2(Arrival=1, Burst=4), P3(Arrival=2, Burst=2). Which process runs at time 3?

AP2

BP1

CP3

DCPU is idle

Step-by-Step Solution

Step 1: At time 0
Only P1 has arrived, so P1 starts running.
Step 2: At time 1
P2 arrives with burst 4, which is less than P1's remaining 7, so preemption occurs and P2 runs.
Step 3: At time 2
P3 arrives with burst 2, less than P2's remaining 3, so preemption occurs and P3 runs.
Step 4: At time 3
P3 has run 1 unit (remaining 1), P2 and P1 are waiting. Since P3 has the shortest remaining time, it continues running.
Final Answer:
Option C -> Option C
Quick Check:
At time 3, the shortest remaining burst is P3's 1 unit, so P3 runs.

Quick Trick: At each arrival, pick the process with the shortest remaining burst [OK]

Common Mistakes:

MISTAKES

Not preempting when a shorter job arrives
Assuming the first process continues until completion

Trap Explanation:

PITFALL

Option B is tempting because P2 arrived before P3, but preemptive SJF always picks the shortest remaining time, so P3 runs at time 3.

Interviewer Note:

CONTEXT

Tests candidate's ability to mentally simulate preemptive SJF scheduling step-by-step.

Master "Shortest Job First (SJF) - Preemptive vs Non-Preemptive" in Operating Systems

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Solution Trace

More Operating Systems Quizzes

Which process runs at time 3?

Step 1: At time 0

Step 2: At time 1

Step 3: At time 2

Step 4: At time 3

Final Answer:

Quick Check:

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