🧠 What is Starvation?
Starvation (also called indefinite blocking) occurs when a process waits endlessly to get the CPU (or any resource) because other higher-priority processes keep getting scheduled ahead of it.
📍 Why Does It Happen?
Starvation usually occurs in priority-based or unfair scheduling algorithms, where:
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The scheduler always favors certain processes (like short jobs or high-priority ones)
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Lower-priority or long-duration processes get ignored
🧩 Real Example
Imagine 5 processes in a system using priority scheduling:
| Process | Priority (lower = better) |
|---|---|
| P1 | 1 |
| P2 | 2 |
| P3 | 3 |
| P4 | 4 |
| P5 | 5 |
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New high-priority processes (P1, P2) keep arriving
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P5 keeps getting postponed — forever!
💀 This is starvation: P5 may never get CPU time
⚠️ Common Causes of Starvation
| Cause | Example |
|---|---|
| 🏷️ Priority Scheduling | Low-priority processes get skipped repeatedly |
| 🔁 Infinite loops of short jobs | In SJF, long jobs may never run |
| 🧺 Resource hogging | A process waits for a resource held by others |
| ⏱️ Improper time quantum | In RR, too small quantum causes too many preemptions |
🧠 Why It’s Dangerous
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Breaks fairness in multi-user systems
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Can cause deadlocks in resource allocation chains
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Critical processes may miss deadlines in real-time systems
🛡️ How to Prevent Starvation
✅ 1. Aging (Dynamic Priority Boosting)
Gradually increase the priority of waiting processes over time
🔧 Example:
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Process P5 starts at priority 5
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Every 10 seconds, priority improves by 1
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Eventually, it becomes top priority
✅ 2. Fair Scheduling Algorithms
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Round Robin
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Multilevel Feedback Queue with aging
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Completely Fair Scheduler (CFS) in Linux
✅ 3. Resource Allocation Limits
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Don’t let one process hold resources for too long
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Enforce maximum wait times
🧠 Interview-Ready Definition:
Starvation is a condition where a process waits indefinitely to be scheduled or to acquire a resource due to unfair allocation policies, such as strict priority or repeated preemption. It can be prevented using techniques like aging, fair scheduling, or time-bound resource policies.
🧠 Bonus One-Liner (🧠 Interview Line):
“Starvation happens when a process is ready to run but never gets the CPU because other processes keep cutting in line — aging is a classic fix.”
🖥️ Real-World Analogy
Imagine you’re waiting in a hospital ER, but they always take more critical patients ahead of you.
You’ve been waiting 10 hours.
New emergencies keep showing up.
You’re starving — not from hunger, but from lack of service.