Both avoid general malloc, but for different patterns. A pool allocates and frees fixed-size blocks individually, you can alloc a block, free it, alloc another, in any order, each O(1) via a free list, ideal for many same-size objects with independent lifetimes (packet buffers, task control blocks, list nodes). An arena (bump/linear allocator) allocates objects of any size by simply advancing a pointer, which is even faster, but there's no individual free, you reclaim memory only by resetting the whole arena at once. Arenas suit batch-scoped work: allocate a burst of temporary state for one frame / one packet / one request, then reset to free it all. So the deciding question is the free pattern: independent per-object lifetimes → pool; allocate-many-then-discard-together → arena. They're often used together (an arena for scratch, pools for long-lived uniform objects).
Data Structures & Algorithms · Interview question
What's the difference between a pool allocator and an arena allocator?
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Static vs Dynamic Allocation
How to give data structures memory on a constrained device: static arrays, fixed-block pools, and arena allocators, the O(1), fragmentation-free alternatives to general malloc.