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The Cost of Indirection in Rust

56 points by sebastianconcpt

by cwillu

1 subcomments

> Maintainability and understandability only show up when you’re deliberate about them. Extracting meaning into well-named functions is how you practice that. Code aesthetics are a feature and they affect team and agentic coding performance, just not the kind you measure in the runtime.
> And be warned: some will resist this and surrender to the convenience of their current mental context, betting they’ll “remember” how they did it. Time will make that bet age badly. It’s 2026 — other AI agents are already in execution loops, disciplined to code better than that.”
Hard disagree: separating code from its context is exactly how you end up in the situation of needing to “remember”. Yes, helper functions and such can be useful for readability, but it's easy to overdo it and end up with incomprehensible ravioli code that does nothing terribly complicated in a terribly complicated manner.

by bombela

1 subcomments

I think this long post is saying that if you are afraid that moving code behind a function call will slow it down, you can look at the machine code and run a benchmark to convince yourself that it is fine?

by ekidd

0 subcomment

We have been able to automatically inline functions for a few decades now. You can even override inlining decisions manually, though that's usually a bad idea unless you're carefully profiling.
Also, it's pointer indirection in data structures that kills you, because uncached memory is brutally slow. Function calls to functions in the cache are normally a much smaller concern except for tiny functions in very hot loops.

by thezipcreator

2 subcomments

seems pointless to extract `handle_suspend` here. There are very few reasons to extract code that isn't duplicated in more than one place; it's probably harder to read to extract the handling of the event than to handle it inline.

by Sytten

0 subcomment

Also to note that the inline directive is optional and the compiler can decide to ignore it (even if you put always if I remember)

by armchairhacker

1 subcomments

A nitpick I have with this specific example: would `handle_suspend` be called by any other code? If not, does it really improve readability and maintainability to extract it?

by cat-whisperer

0 subcomment

I wouldn't have agreed with you a year ago. async traits that were built with boxes had real implications on the memory. But, by design the async abstraction that rust provides is pretty good!

0 subcomment

by Scubabear68

2 subcomments

A function call is not necessarily an indirection. Basic premise of the blog is wrong on its face.

by slopinthebag

1 subcomments

Cool article but I got turned off by the obvious AI-isms which, because of my limited experience with Rust, has me wondering how true any of the article actually is.