If a system using FCFS scheduling introduces a mix of I/O-bound and CPU-bound processes arriving at different times, how does this affect the convoy effect and waiting times, and what strategy could reduce the negative impact?
hard🎤 Interviewer Follow-up Q15 of Q15
Operating Systems - FCFS Scheduling - Convoy Effect & Waiting Time
If a system using FCFS scheduling introduces a mix of I/O-bound and CPU-bound processes arriving at different times, how does this affect the convoy effect and waiting times, and what strategy could reduce the negative impact?
AThe convoy effect disappears because I/O-bound processes run first, so waiting times decrease automatically
BThe convoy effect worsens as CPU-bound processes block I/O-bound ones, increasing waiting times; introducing preemption can help
CWaiting times remain unchanged because FCFS ignores process type and arrival time
DThe convoy effect is irrelevant in mixed workloads since I/O-bound processes do not use the CPU
Step-by-Step Solution
Step 1: Understand process types in FCFS
FCFS schedules strictly by arrival order, regardless of process type.
Step 2: Analyze impact of mixed workloads
CPU-bound processes arriving first can delay I/O-bound processes, worsening the convoy effect and increasing waiting times.
Step 3: Mitigation strategy
Introducing preemption or priority scheduling can reduce waiting times for I/O-bound processes by allowing them to run sooner.
Step 4: Evaluate options
A is incorrect; convoy effect does not disappear automatically. B is correct; convoy effect worsens and preemption helps. C is incorrect; waiting times do change due to process mix. D is incorrect; convoy effect is relevant because all processes compete for CPU.
Final Answer:
Option B -> Option B
Quick Check:
Mixed workloads worsen convoy effect; preemption mitigates it.
Assuming I/O-bound processes run first automatically
Believing waiting times don't change with process mix
Ignoring convoy effect in mixed workloads
Trap Explanation:
PITFALL
Option A is tempting because I/O-bound processes often block less, but FCFS does not prioritize them. Option C ignores the impact of process mix on waiting times. Option D wrongly claims convoy effect is irrelevant.
Interviewer Note:
CONTEXT
Tests deep understanding of convoy effect in realistic mixed workloads and mitigation strategies.
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