Benchmark Lock-Free vs Mutex-Based Queue Under High Contention

Pick the Right Synchronization

Lock-free structures shine under moderate contention and small critical sections. Mutexes plus a simple queue often win when critical sections are large, when you need condition variables, or when every core hammers the same CAS cache line.

Decision Factors

Measure throughput and tail latency, not ideology. Consider memory reclamation cost, programmer complexity, and priority inversion requirements.

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• perf stat -e cache-misses on CAS loops shows line bouncing
• Lock-free does not mean wait-free; starvation is still possible
• Real-time systems may prefer mutex with priority inheritance
• Profile both implementations on your actual core count

Working Through the Exercise

Keep the relevant documentation open while you implement. When your output disagrees with the reference, trace one failing case by hand before changing random lines.

• Trace first: walk one failing input step by step
• Read the manual: skim the official doc for the mechanism named in this task
• Compare baselines: save measurements from the prior step so speedups are honest

Why for this exercise

You will benchmark lock-free queue vs mutex-backed queue under increasing thread counts. This exercise requires plotting where each approach wins and explaining the crossover.