It seems that this would be a great reason to not pass the entire heavy object through your function, and to instead pass it as a reference. When passing an ob

It seems that this would be a great reason to not pass the entire heavy object through your function, and to instead pass it as a reference. When passing an object (rather than a reference to an object) there's a lot more work going on both in function setup, and in object dropping. I'm not a rust guru, so I don't know the precise wording, but it's simple enough to realize that if this function, as claimed, must drop all the sub-objects within the `HeavyObject` type, then those objects must have been copied from the original object. If you instead define the function to take in a reference (by adding just two `&` characters into your program), the single-threaded case is now almost 100x faster than the multithreaded case. Here's a link to a Rust Playground with just those two characters changed: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=9bbe169c77cd31b6cd25b74c24635e12 https://play.rust-lang.org/?version=stable&mode=debug&editio... Note that the code that drops the data in a separate thread is not timing the amount of time your CPU is spinning, dropping the data. So while this does decrease the latency of the original thread, the best solution is to avoid copying and then freeing large, complex objects as much as possible. While it is of course necessary to do this sometimes, this particular example is just not one of them. :) As an aside, I'm somewhat surprised that the Rust compiler isn't inlining and eliminating all the copying and dropping; this would seem to be a classic case where compiler analysis should be able to determine that `a.size()` should be computable without copying `a`, and it should be able to eliminate the function call cost as well. Manually doing this gives the exact same timing as my gist above, so I assume that this is happening when passing a reference, but not happening when passing the object itself.