> 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.
Each part of the codebase is a separate self contained module with its own wrapping (boilerplate), except there's like 30 of them and you still have to understand everything as a whole to understand the behaviour of the system anyway.
Think of what ravioli are and apply that to the same code analogy as spagetti or lassagna. The code is split in tiny units and that creates too much indirection, a different indirection than spagetti or ravioli. The architecture feels fragmented even though there's nothing wrong with each piece.
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?
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.
I'm not sure Rust's `async fn` desugaring (which involves a data structure for the state machine) is inlineable. (To be precise: maybe the desugared function can be inlined, but LLVM isn't allowed to change the data structure, so there may be extra setup costs, duplicate `Waker`s, etc.) It's probably true that there is a performance cost. But I agree with the article's point that it's generally insignificant.
For non-async fns, the article already made this point:
> In release mode, with optimizations enabled, the compiler will often inline small extracted functions automatically. The two versions — inline and extracted — can produce identical assembly.
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.
The logic of process flow is essentially one kind of information.
All the implementation details are another.
Step functions should not hide further important steps - they should only hide hairy implementation details that other steps don't need to know about.
There's extraction for reuse and then theres extraction for readability/maintainability. The second largely comes down to personal taste. I personally tend to lose the signal in the noise, so it's easy for me to follow the logic if some of the larger bits are pushed into appropriately named functions. Goes to the whole self commenting code thing. I know there's a chunk of code behind that function call, I know it does some work based on its name and args, but I don't have to worry about it in the moment. There's a limit of course, moving a couple lines of code out without good cause is infuriating.
Other people prefer to have big blocks of code together in one place, and that's fine too. It just personally makes it harder for me to track stuff.
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!
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?
The idea is that performance isn’t a reason not to do it. Other considerations may cause you to choose inline, but performance shouldn’t be one of them.
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.
People new to Rust sometimes assume every abstraction is free but that's just not the case, especially with lifetimes and dynamic dispatch. Even a small function call can hide allocations or vtable lookups that add up quickly if you're not watching closely.
> 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.
I’m familiar with spaghetti code and with lasagna code (too many layers) but I’m curious: what’s ravioli code?
Each part of the codebase is a separate self contained module with its own wrapping (boilerplate), except there's like 30 of them and you still have to understand everything as a whole to understand the behaviour of the system anyway.
Think of what ravioli are and apply that to the same code analogy as spagetti or lassagna. The code is split in tiny units and that creates too much indirection, a different indirection than spagetti or ravioli. The architecture feels fragmented even though there's nothing wrong with each piece.
a ravioli is a b̶l̶a̶c̶k̶ beige box abstraction to which you pasta arguments interface usually after forking
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?
I think it’s making a case that normally you shouldn’t even bother benchmarking it, unless you know that it’s in a critical hot path.
I must add that code is on the hot path only under two conditions:
- the application is profiled well enough to prove that some piece of code is on the hot path
- the developers are not doing a great job
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.
I'm not sure Rust's `async fn` desugaring (which involves a data structure for the state machine) is inlineable. (To be precise: maybe the desugared function can be inlined, but LLVM isn't allowed to change the data structure, so there may be extra setup costs, duplicate `Waker`s, etc.) It's probably true that there is a performance cost. But I agree with the article's point that it's generally insignificant.
For non-async fns, the article already made this point:
> In release mode, with optimizations enabled, the compiler will often inline small extracted functions automatically. The two versions — inline and extracted — can produce identical assembly.
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.
I strongly prefer this sort of code:
```
} ```The logic of process flow is essentially one kind of information. All the implementation details are another. Step functions should not hide further important steps - they should only hide hairy implementation details that other steps don't need to know about.
One huge one is so that you can test it in isolation.
There's extraction for reuse and then theres extraction for readability/maintainability. The second largely comes down to personal taste. I personally tend to lose the signal in the noise, so it's easy for me to follow the logic if some of the larger bits are pushed into appropriately named functions. Goes to the whole self commenting code thing. I know there's a chunk of code behind that function call, I know it does some work based on its name and args, but I don't have to worry about it in the moment. There's a limit of course, moving a couple lines of code out without good cause is infuriating.
Other people prefer to have big blocks of code together in one place, and that's fine too. It just personally makes it harder for me to track stuff.
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)
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!
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?
The idea is that performance isn’t a reason not to do it. Other considerations may cause you to choose inline, but performance shouldn’t be one of them.
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.
I don't see anything wrong code-wise, but it's definitely an odd way of making an accumulator. Maybe I'm pedantic
A function call is not necessarily an indirection. Basic premise of the blog is wrong on its face.
People new to Rust sometimes assume every abstraction is free but that's just not the case, especially with lifetimes and dynamic dispatch. Even a small function call can hide allocations or vtable lookups that add up quickly if you're not watching closely.
Did you read the article? The author makes exactly that point.