That's the point. With an arena allocator, you don't "really" de-allocate the OS memory, you just free the bytes to be re-used again in the next iteration (by using a FixedBufferAllocator as the backing allocator, if you know how much memory will be needed in advance). This is much better than trying to re-use the structs manually as the OP mentioned at the end.

EDIT: FixedBufferAllocator has a reset method , so maybe you just need to use that to "free" all memory on each iteration? Perhaps using that directly is enough if you know the max memory usage at compile-time... I was just thinking that it should be possible to use an arena allocator to basically tell the delegate allocator to make all memory available again without freeing it back to the OS?! If anyone knows more about allocators I would be happy to know this. https://ziglang.org/documentation/master/std/#A;std:heap.Fix...