COS3721 Assignment 2 (COMPLETE ANSWERS) 2026

COS3721
ASSIGNMENT 2 2026

UNIQUE NO.
DUE DATE: 1 JULY 2026

,OPERATING SYSTEMS

Question 01 [15 marks]

a. Scheduling approaches

Per-core run queues:

 Each CPU core maintains its own queue of ready processes.
 CPU-intensive tasks tend to stay on the same core, improving cache locality.
 Interactive tasks may suffer if stuck behind longer tasks in the same queue.

Shared run queue:

 All processes are placed in a single global queue.
 Any idle core can pick the next available task.
 Improves responsiveness for short interactive tasks due to flexible scheduling.



b. Advantages and disadvantages

Per-core run queues

Advantages:

 Better CPU cache locality (tasks stay on same core)
 Reduced queue contention

Disadvantages:

 Load imbalance between cores
 Requires complex load balancing

Shared run queue

, Advantages:

 Good load balancing across cores
 Better responsiveness for interactive tasks

Disadvantages:

 High contention on shared queue
 Poor cache locality due to task migration



c. Load imbalance scenario

The shared run queue is better for balancing workload because:

 All cores draw from a single pool of tasks.
 Idle cores can immediately fetch tasks.
 Prevents some cores from being overloaded while others are idle.



d. Recommendation

Recommended: Per-core run queues with load balancing

 High performance due to reduced contention
 Better cache efficiency (CPU-bound tasks remain on same core)
 Fairness ensured through periodic task migration
 Suitable for mixed workloads (interactive + CPU-intensive)




Question 02 [15 marks]