Operating Systems - TLB - Translation Lookaside Buffer & Effective Access Time
In a system where the TLB hit ratio is extremely low due to random memory accesses, which approach is likely to yield better Effective Access Time (EAT)?
In a system where the TLB hit ratio is extremely low due to random memory accesses, which approach is likely to yield better Effective Access Time (EAT)?
hard⚖️ Approach Comparison Q8 of Q15
Step-by-Step Solution
Solution:
Step 1: Understand low TLB hit ratio impact
Low hit ratio means TLB lookups rarely help, so TLB overhead may not justify gains.Step 2: Evaluate options
A: Correct -- multi-level page tables reduce page table lookup time, improving EAT despite low TLB hits.
B: Incorrect -- increasing TLB size may not help much if accesses are random; hit ratio gains minimal.
C: Incorrect -- disabling TLB removes caching benefit and still requires page table walks.
D: Incorrect -- page replacement optimization affects page faults, not TLB hit ratio or lookup time.Final Answer:
Option A -> Option AQuick Check:
Multi-level page tables reduce lookup overhead when TLB misses dominate [OK]
Quick Trick: Low TLB hit -> optimize page table lookup, not TLB size [OK]
Common Mistakes:
MISTAKES- Assuming bigger TLB always helps
- Thinking disabling TLB improves performance
- Confusing page fault reduction with TLB effectiveness
Trap Explanation:
PITFALL- Candidates often try to fix low hit ratio by increasing TLB size ignoring diminishing returns.
Interviewer Note:
CONTEXT- Tests ability to apply TLB knowledge to corner cases and trade-offs.
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