you ' ve got to be fucking kidding me . <| sep |> Americans do that to Americans depending on what state you ' re from . <| sep |> I think you meant nigger editNigger noun bundle of sticks why is this being downvoted ? <| sep |> Wow , that was a very bad kick . <| sep |> Indeed , if you know you will insert more elements you can reserve the space before inserting . If you change the snippet of code in the article for use s t d collectionshashsetHashSet fn main println ! populating . let mut one HashSetnew for i in 1 . 5000000 one . inserti println ! cloning . let mut two HashSetwithcapacityone . capacity Reserve enough space in the second hashmap right away for v in one two . insertv Both loops finish very quickly , and you don ' t see this behaviour at all . The problem is when an attacker is purposely trying to trigger this behaviour , in scenarios more complex than this one and that can ' t be so easily solved .