I recently discovered `macro-stats` (The awesome tool developed by u/nnethercote) and applied it to one of the slowest projects I'm working on.

It provides helpful stats about macros in your crate. How many lines or bytes they're generating and how many times they're used.

This makes it easier to identify optimization opportunities that can significantly reduce compile time.

Let me walk you through what I tried:



**Project setup:**

The project has a separate crate mainly for models and repositories. The Diesel schema file was also part of that crate.



**Baseline:**

Incremental compilation of the crate, for adding one-space in a file, took about **9.68**s.

And there were **434,770** total macro-generated lines (see screenshot).



**First optimization:**

The main optimization point could be the Diesel schema file. So I moved it to its own crate. Then the one-space-to-a-file compile time and macro total lines changed to **6.44**s and **228,729**. About **1.5x** faster than the original compile time. 🎉



**Second optimization:**

Next, I noticed a lot of macro lines coming from `tracing`, which we don't really need during development. So I introduced a feature flag to conditionally include `tracing`. After this change, the one-space-to-a-file compile time and macro total lines changed to **3.72**s and **131,440**. About **2.5x** faster than the original compile time. ⚡  


**Try it yourself:**

Give it a try and run the following command to inspect your crates:

`cargo +nightly rustc -- -Zmacro-stats`

(or something similar for your specific project)



Let me know if it helps you cut down compile times!



[Media] Improving Rust Compile Time with macro-stats 🚀