Comment by josephg
2 days ago
Disabling codegen units = 1 speeds up the compilation further. But it’s still too many dependencies and too slow. The binary is pretty huge too.
2 days ago
Disabling codegen units = 1 speeds up the compilation further. But it’s still too many dependencies and too slow. The binary is pretty huge too.
> But it’s still too many dependencies and too slow.
I definitely agree that it's too slow. I just don't think the cause is "too many dependencies" because I've compiled Rust codebases with twice as many dependencies in half the time!
It seems to produce a 94MB binary. So it may be partly that there are some very big dependencies. But the amount of compilation time that ends up in the top-level crate (even with LTO disabled) also makes me feel like this must be triggering a compiler bug. Either that or using far too many generics.
I agree it's probably monomorphization (speculation without looking at it). Generic function parameters might be the root cause, but number of dependencies is a combinatorial multiplier.
I've hit compiler bugs that behave this way. Here's one from an LLVM upgrade [1]. The test case I discovered apparently took over 20 minutes to compile, up from 26 seconds on stable! Their value tracking algorithm was accidentally quadratic.
[1]: https://github.com/rust-lang/rust/issues/137909
> But it’s still too many dependencies and too slow. The binary is pretty huge too.
Ah yes, my never-ending crusade to raise awareness that the cost of free (as in effort) dependencies is bloat.
You can make useful tools that are tiny and compile fast [1], but it takes a lot of effort; exactly what developers don't want to spend.
[1]: Like https://github.com/parasyte/hd -- And I wrote about one of the tricks that it uses: https://blog.kodewerx.org/2023/04/improving-build-times-for-...