Started with a linear scan first-fit approach, which took me maybe 25 minutes.
Start by clarifying assumptions (e.g., single-threaded, no coalescing initially) and implement a simple free list allocator with malloc and free. Then iteratively optimize by adding splitting, coalescing, segregated free lists, and possibly a slab allocator for small sizes, discussing trade-offs at each step.
Pro tip: Demonstrate awareness of real-world allocator design by mentioning alignment, fragmentation, and performance metrics; also discuss how you would test and benchmark your allocator against system malloc.
Ask about the environment: single-threaded vs multi-threaded, expected allocation sizes, performance goals, and whether alignment or debugging features are needed.
Implement a simple free list allocator using a linked list of free blocks, with malloc finding a suitable block and free adding it back. Include metadata for block size and status.
Introduce splitting to reduce internal fragmentation and coalescing to reduce external fragmentation. Consider boundary tags for efficient coalescing.
Implement segregated free lists (size classes) for faster allocation, and a slab allocator for small objects to reduce overhead. Discuss trade-offs like memory overhead vs speed.
Benchmark against system malloc using metrics like throughput, fragmentation, and memory utilization. Discuss further optimizations like thread-local caches or lock-free structures if needed.
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