1. Introduction to CPU Scheduling
In a multiprogramming system, multiple processes compete for the CPU. Since only one process can execute at a time, the CPU scheduler decides which process to run next to maximize CPU utilization and system performance.
💡 Why is CPU Scheduling Important?
- Efficient CPU utilization – Prevents CPU from sitting idle.
- Faster execution – Reduces waiting time for processes.
- Improves multitasking – Ensures smooth switching between tasks.
- Prevents starvation – Ensures all processes get CPU time.
2. Why is CPU Scheduling Needed?
📌 1. Limited CPU Resources
✅ Only one process can execute on the CPU at a time.
✅ The CPU scheduler selects the best process from the ready queue.
✔ Example:
- If 10 processes are waiting, the scheduler prioritizes execution based on scheduling policies.
📌 2. Process Execution Types
Processes alternate between CPU and I/O operations.
- CPU-bound process → Needs more CPU time (e.g., video processing).
- I/O-bound process → Spends more time on I/O (e.g., file reading).
✅ The scheduler optimally switches between these processes to improve efficiency.
✔ Example:
- A video encoder (CPU-bound process) should not block an email client (I/O-bound process) from running.
📌 3. Reduce Waiting Time & Response Time
✅ Proper CPU scheduling reduces the waiting time of processes in the queue.
✅ It ensures faster response time in interactive systems.
✔ Example:
- Without scheduling, a low-priority process may wait indefinitely while others execute.
📌 4. Achieve Multiprogramming & Time-Sharing
✅ CPU scheduling enables multiprogramming, allowing multiple processes to run simultaneously.
✅ Time-sharing systems allow multiple users to share CPU resources fairly.
✔ Example:
- In a banking system, multiple users perform transactions on the same server.
📌 5. Prevent CPU Starvation & Deadlocks
✅ Ensures that all processes get CPU time fairly.
✅ Prevents low-priority tasks from being ignored indefinitely.
✔ Example:
- If only high-priority processes execute, low-priority processes never run, leading to starvation.
3. Goals of CPU Scheduling
| Goal | Description |
|---|---|
| Maximize CPU Utilization | Ensure CPU is always busy, avoiding idle time. |
| Minimize Waiting Time | Reduce time spent by processes in the ready queue. |
| Minimize Turnaround Time | Ensure faster completion of processes. |
| Minimize Response Time | Improve system responsiveness, especially in interactive environments. |
| Fairness | Ensure that all processes get a fair share of CPU time. |
4. Conclusion
✔ CPU Scheduling is essential for efficient CPU usage and system performance.
✔ It ensures fair execution of processes, prevents starvation, and improves responsiveness.
✔ Schedulers like FCFS, SJF, Round Robin, and Priority Scheduling help in achieving these goals.