Arena allocation is useful when many objects have the same known lifetime. An example from games is per-frame allocations. All objects needed only for the frame

Arena allocation is useful when many objects have the same known lifetime. An example from games is per-frame allocations. All objects needed only for the frame being rendered are carved out of a large chunk of preallocated memory. The chunk is reused every frame instead of being freed back to the system allocator. In addition to the performance benefits, this results in less memory fragmentation.