Memory cost of sending items over mpsc channel

Question

I have two threads that read a stream of messages from two sources and then forward them to a third sink where they get processed in order.

I'm concerned about the overhead of copying data as my messages are on each thread's stack and to move them through mpsc , every bit has to be copied over to the sink's stack.

If I try to mitigate this by putting my message in a Box , then only the pointer would be sent over to the new stack but still a copy happens from source's stack to heap.

And I'm not entirely sure if my message is on heap or stack, as I saw a blog post in rust-lang.org the other day which claimed a vec,[1,2,3] lives on stack, which if true, is something I wouldn't have guessed.