I believe the Ord docs do cover this: This trait can be used with #[derive]. When derived on structs, it will produce a lexicographic ordering based on the top-to-bottom declaration order of the struct's members. When derived on enums, variants are ordered by their top-to-bottom declaration order. And so, in your example, the struct has 1 vec element to compare and the documentation search now needs to continue over in Vec to see how it implements Ord and it's there that you hit the perf concerns you care about.