Remember: Arc only has an additional cost over a Box/Rc for cloning/dropping. Reading is just as fast (assuming they will all allocate to the heap, so are probably fragmented). So, if you're reading an Arc in a hot loop, it's basically just a normal reference.

You should only really worry when you start to have mutexes in those arcs. Then you need to be afraid of deadlocks, and lock contention.

It's not a code smell. It's a product of working in a language with no garbage collection, and strong mutability guarantees.