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Implement Demand Paging: Allocate on First Access

hard5/10

Implement mmap Semantics: Map Region and Handle Page Faults Implement Copy-on-Write (COW) for fork() Efficiency

Language

Compiler

2.0s Limit 256MB

Implementation

Implement demand paging simulation.

Requirements:

Page table with present bit (initially 0)
Page fault handler allocates frame
Track allocated pages count
Access to page triggers allocation
Print page fault statistics
Show memory savings vs eager allocation

Test:

Large mmap() with sparse access
Only accessed pages allocated
Count page faults

Why This Matters

Demand paging is why touching one byte of a 1GB anonymous mmap doesn't cost 1GB of resident memory up front — Linux's memory overcommit accounting and every sparse-array workload depend on exactly this lazy-allocation behavior. Get the present-bit check backwards and every access becomes an unnecessary page fault, or worse, a real fault is silently skipped and you read unallocated memory.

Hints

0 / 3 revealed

Validation Suite

main.c

Workspace 1.0