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.
One of the unwritten takeaways of this post is that async/await is a leaky abstraction. It's supposed to allow you to write non-blocking I/O as if it were blocking I/O, and make asynchronous code resemble synchronous code. However, the cost model is different because async/await compiles down to a state machine instead of a simple call and return. The programmer needs to understand this implementation detail instead of pretending that async functions work the same way as sync functions. According to Joel Sposky, all non-trivial abstractions are leaky, and async/await is no different. [0]
The article mixes together two distinct points in a rather muddled way. The first is a standard "premature optimization is the root of all evil" message, reminding us to profile the code before optimizing. The second is a reminder that async functions compile down to a state machine, so the optimization reasoning for sync functions don't apply.
[0] https://www.joelonsoftware.com/2002/11/11/the-law-of-leaky-a...
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!
The author is right about inlining but has picked the wrong example to show this since the compiler cannot inline across await.
If this function is in the hot path the last thing you'll want to do is to needlessly call await. You'll enter a suspension point and your task can get migrated to another thread. It is in no way comparable to the dead simple inlining example given later.
This is why you should always benchmark before making guesses, and to double check you're even benchmarking the right thing. In this case they used the findings from a nonasync benchmark and applied it to async. This will lead you to a very wrong conclusion, and performance issues.
Regardless of the language, optimisation of this kind has always been a trap for me when moving back and forth between old or otherwise small, embedded systems and modern hardware and toolchains. When we were learning C, compilers weren't as smart as they are today, and every little bit helped - old habits die hard. The lesson is simple - just see what the compiler does with your code first. But also, weigh the real performance pinch points vs. readability and convenience, and as much as it's tempting, don't optimise prematurely - of course I always do; its fun.
A function call is not necessarily an indirection. Basic premise of the blog is wrong on its face.
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.
in a nutshell: clear defined helper functions are much better for comprehension than bigger functions. and they usually cost nothing ar runtime sine the compiler inlines them anyway.
But the real cost is that having a myriad of them is usually very difficult to get the right cut. not too small not too big and having a clear intend of what it exactly does.
so nothing new. API design is hard. naming thing even more so.
I love how this post, almost to a fault, just jumps right in. No BS set up. Not even context set up. Just what you expected after reading the title. That's an art.
As for the context of the article, maintainability is almost always worth the cost of the function lookup. The proof here that the cost is almost non-existent means to me the maintainability is always worth the perceived (few cycles) impact unless this is real-time code.
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?
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.
> 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.