Operating Systems - Context Switch - Cost & Causes
Why does increasing the frequency of context switches beyond a certain point degrade overall system performance?
Why does increasing the frequency of context switches beyond a certain point degrade overall system performance?
medium🪤 Complexity Trap Q13 of Q15
Step-by-Step Solution
Step 1: Identify overhead of context switch
Saving/restoring CPU registers and PCB updates consume CPU time, causing overhead.Step 2: Scheduler availability
The scheduler can always select processes; running out is not a cause of performance degradation.Step 3: MMU and page tables
MMU page table reloads happen on address space switches, but not necessarily on every context switch.Step 4: CPU cache behavior
CPU cache is not flushed automatically on every context switch; cache invalidation is more complex.Final Answer:
Option A -> Option AQuick Check:
Context switch overhead is mainly CPU cycles spent saving/restoring registers.
Quick Trick: More switches -> more register save/restore overhead -> slower system [OK]
Common Mistakes:
MISTAKES- Believing scheduler runs out of processes
- Assuming MMU reloads page tables every switch
- Thinking CPU cache flushes on every context switch
Trap Explanation:
PITFALL- Options B, C, and D are plausible but incorrect causes of performance degradation due to context switching.
Interviewer Note:
CONTEXT- Tests understanding of the cost and trade-offs of context switching frequency.
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