I would suggest you read the source code of Mutex <https://doc.rust-lang.org/src/std/sync/mutex.rs.html#178-182> and then of UnsafeCell <https://doc.rust-lang.org/std/cell/struct.UnsafeCell.html>.

So, the layout of Mutex<T> is the same as T and then some lock (well, obviously).

>Rust introduces an extra layer of pointer indirection with Mutex, which can hurt performance significantly with cache misses.

Why would there be an extra pointer dereference? There isn't.