> One of the biggest issues with reference counting, from a performance perspective, is that it turns reads into writes: if you read a heap-object out of a data

> One of the biggest issues with reference counting, from a performance perspective, is that it turns reads into writes: if you read a heap-object out of a data structure, you have to increment the object's reference count. This is one of the biggest misconception about RC. You need not to increase the refcount just to read the referred data because you already have a reference whose count has been increased when handed down to you. That’s a semantic that’s very well carried off by Rust’s Arc type: the count is inc’ when the Arc is cloned, and dec’ when the cloned Arc is dropped. But you can still get a regular ref to the data since the compiler will be able to enforce locally the borrow, ownership and lifetime rules. For example, in a web server, you might have the app’s config behind an Arc. It gets cloned for each request (thus rc inc’d), read a lot during the req, then dropped (thus rc dec’d) at the end of the handler.