Operating Systems - System Call - Mechanism & Modes (User vs Kernel)
What is the primary reason that excessive transitions between user mode and kernel mode during system calls can negatively impact system throughput?
What is the primary reason that excessive transitions between user mode and kernel mode during system calls can negatively impact system throughput?
medium💡 Conceptual Thinking Q5 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand mode switching overhead
Switching from user to kernel mode requires saving the current CPU context and loading kernel context.Step 2: Analyze impact on performance
This context saving/restoring consumes CPU cycles, increasing latency for each system call.Final Answer:
Option D -> Option DQuick Check:
Mode switch overhead causes performance degradation [OK]
Quick Trick: Mode switches add CPU overhead due to context saving [OK]
Common Mistakes:
MISTAKES- Assuming kernel mode is always slower than user mode
- Believing user mode cannot handle concurrent system calls
- Thinking mode switches permanently change CPU privileges
Trap Explanation:
PITFALL- Option B looks plausible but kernel mode instructions are not inherently slower.
Interviewer Note:
CONTEXT- Tests understanding of system call overhead and CPU mode switching costs.
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