How Free-List, Slab, and Buddy Allocators Solve Memory Management Challenges

A developer tutorial series exploring OS memory allocation explains how page-based memory management introduces new challenges around efficiency and overhead. Modern 64-bit CPUs read data in 8-byte chunks, making memory alignment critical for performance, though page-aligned memory from the OS helps address this. A key problem arises with small allocations, where metadata overhead can exceed 600% of the actual memory requested. The Linux kernel addresses this with Slab Allocators, which use a single control structure to manage hundreds of fixed-size slots. The article introduces three main allocator strategies — Slab, Buddy, and Free-List — each suited to different use cases, and demonstrates a basic Free-List implementation using linked lists and pointer arithmetic in C.