GATE CS 2022 Q.38: Memory Management and Virtual Memory

Which one of the following statements is FALSE?

The TLB performs an associative search in parallel on all its valid entries using page number of incoming virtual address.

If the virtual address of a word given by CPU has a TLB hit, but the subsequent search for the word results in a cache miss, then the word will always be present in the main memory.

The memory access time using a given inverted page table is always same for all incoming virtual addresses.

In a system that uses hashed page tables, if two distinct virtual addresses V1 and V2 map to the same value while hashing, then the memory access time of these addresses will not be the same.

Official answer and solution

Official answer: C
From: Official GATE 2022 answer key

Solution

Analyze the operational properties of Translation Lookaside Buffers, inverted page tables, and hashed page tables.

Evaluating each statement:

(A) TRUE: The TLB is implemented using associative (content-addressable) memory where all valid entries are compared in parallel against the virtual page number.
(B) TRUE: A TLB hit means the page table has mapped the virtual page to a valid physical frame residing in main memory. If a subsequent cache search misses, the CPU fetches the word from that main memory frame.
(C) FALSE: An inverted page table is typically searched using a hash anchor table with collision chains. Virtual addresses whose page numbers hash to buckets with collisions must traverse linked lists of varying lengths, so memory access times vary across virtual addresses.
(D) TRUE: In hashed page tables, collisions require traversing a chain of entries, which causes addresses with collisions to have longer search times than those without collisions.

Final answer

Option (C)

Common trap

Thinking an inverted page table provides constant-time access for all addresses without considering hash collisions.

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2022 Computer Science and Information Technology (CS)
Question: 38 of 65
Section: Computer Science and Information Technology

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