GATE CS 2024 Set 2 Q.24: Memory Management and Virtual Memory

Which of the following tasks is/are the responsibility/responsibilities of the memory management unit (MMU) in a system with paging-based memory management?

Allocate a new page table for a newly created process

Translate a virtual address to a physical address using the page table

Raise a trap when a virtual address is not found in the page table

Raise a trap when a process tries to write to a page marked with read-only permission in the page table

Official answer and solution

Official answer: B, C and D
From: Official GATE 2024 answer key

Solution

Identify which paging operations are performed in hardware by the MMU versus in software by the operating system kernel.

The Memory Management Unit (MMU) is the hardware component responsible for runtime virtual-to-physical address translation and permission checking on every memory access:

(A) is FALSE: Allocating and initializing a page table for a new process is a software task performed by the OS kernel.
(B) is TRUE: The MMU translates virtual addresses into physical addresses by consulting the TLB and walking the page table.
(C) is TRUE: When the valid/present bit of a page table entry is 0 (page not in main memory or unmapped), the MMU raises a page-fault trap to the OS.
(D) is TRUE: When a write access targets a page whose PTE permission bits mark it as read-only, the MMU raises a protection fault/trap to the OS.

Final answer

Options (B), (C), (D)

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

Source

Paper: GATE 2024 Computer Science and Information Technology - Set 2 (CS2)
Question: 24 of 65
Section: Computer Science and Information Technology

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