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If the frequency of context switches doubles in a system, how does this affect the overall CPU overhead due to context switching, assuming each switch has a fixed cost?

medium🪤 Complexity Trap Q5 of Q15

Operating Systems - Context Switch - Cost & Causes

If the frequency of context switches doubles in a system, how does this affect the overall CPU overhead due to context switching, assuming each switch has a fixed cost?

ACPU overhead remains the same because context switch cost is amortized over time.

BCPU overhead doubles because overhead is proportional to the number of context switches.

CCPU overhead halves because processes run shorter bursts reducing overhead per process.

DCPU overhead increases but less than double due to caching effects.

Step-by-Step Solution

Solution:

Step 1: Understand overhead proportionality
Each context switch has a fixed cost; doubling switches doubles total overhead.
Step 2: Evaluate other options
Overhead does not remain the same; it scales with switch count. Overhead does not halve; it increases. Caching effects do not significantly reduce context switch overhead.
Final Answer:
Option B -> Option B
Quick Check:
Overhead ∝ number of context switches [OK]

Quick Trick: Overhead scales linearly with context switch count [OK]

Common Mistakes:

MISTAKES

Assuming overhead amortizes away
Believing shorter runs reduce overhead
Thinking caching reduces context switch cost

Trap Explanation:

PITFALL

Candidates often underestimate overhead growth, thinking amortization or caching helps.

Interviewer Note:

CONTEXT

Tests understanding of overhead scaling with context switch frequency.

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