Operating Systems - Context Switch - Cost & Causes
Imagine a system where a context switch occurs every 5 milliseconds. If the context switch overhead is 0.5 milliseconds, what is the effective CPU time available for processes in each 5 ms interval?
Imagine a system where a context switch occurs every 5 milliseconds. If the context switch overhead is 0.5 milliseconds, what is the effective CPU time available for processes in each 5 ms interval?
easy🧠🧾 Concept Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Calculate effective CPU time
Each 5 ms interval includes 0.5 ms overhead for context switching, so usable CPU time = 5 ms - 0.5 ms = 4.5 ms.Step 2: Check other options
5 milliseconds ignores overhead. 0.5 milliseconds mistakes overhead as usable time. 4 milliseconds subtracts 1 ms incorrectly.Final Answer:
Option D -> Option DQuick Check:
Subtract overhead from total interval [OK]
Quick Trick: Subtract context switch overhead from total interval [OK]
Common Mistakes:
MISTAKES- Ignoring overhead in calculation
- Confusing overhead as usable time
- Incorrect subtraction amount
Trap Explanation:
PITFALL- Candidates often forget to subtract overhead or confuse overhead with usable CPU time.
Interviewer Note:
CONTEXT- Tests ability to reason about overhead impact on CPU availability.
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