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Trace the sequence of events when a memory allocation request cannot be satisfied due to external fragmentation, even though total free memory is sufficient.

easy🧠🧾 Concept Trace Q12 of Q15
Operating Systems - Internal vs External Fragmentation - Compaction & Buddy System
Trace the sequence of events when a memory allocation request cannot be satisfied due to external fragmentation, even though total free memory is sufficient.
AInternal fragmentation increases to accommodate the request in smaller blocks
BThe system immediately rejects the request without attempting any memory rearrangement
CThe buddy system automatically merges all free blocks regardless of their sizes to fulfill the request
DThe system performs compaction to consolidate free memory blocks before retrying allocation
Step-by-Step Solution

  1. Step 1: Identify external fragmentation effect

    External fragmentation means free memory is split into small noncontiguous blocks.

  2. Step 2: Understand system response

    Compaction rearranges memory to create larger contiguous free blocks, enabling allocation.

  3. Step 3: Evaluate other options

    Immediate rejection (B) ignores compaction; buddy system merges only buddies, not all blocks (C); internal fragmentation (D) is unrelated to external fragmentation.

  4. Final Answer:

    Option D -> Option D

  5. Quick Check:

    Compaction is the standard response to external fragmentation [OK]
Quick Trick: External fragmentation -> compaction to consolidate free space [OK]
Common Mistakes:
MISTAKES
  • Assuming buddy system merges all free blocks automatically
  • Believing internal fragmentation can solve external fragmentation
  • Thinking system rejects requests without compaction
Trap Explanation:
PITFALL
  • Option C confuses buddy system merging rules; B ignores compaction; D mixes internal and external fragmentation concepts.
Interviewer Note:
CONTEXT
  • Checks candidate's understanding of system behavior when external fragmentation blocks allocation despite enough total free memory.
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