Rust compiler gets 4.57% faster in two months, with 555 benchmarks improving
How to speed up the Rust compiler in September 2026
Rust compiler performance improved by 4.57% in mean wall-time between July and September 2026, with 555 of 629 benchmarks showing gains. Key contributors include PGO for Clippy, LLVM 23, and optimizations to the new borrow checker and trait solver. The author also highlights a dataflow analysis change that cut compile time by 30% on a large crate. He will join Hexcat to work on compiler performance.
The mean wall-time reduction was 4.57%, which is a remarkable improvement in just two months. Of the 629 benchmark measurements, 555 of them improved and only 74 regressed.
- knuckleheads
Funny to see this now. I’ve got a private branch I am in the process of shaping up this weekend to show the compiler team. For deep nested projects like rust analyzer, if you emit the meta data about function types earlier for downstream slots to use, before successful type checking, you can start other crates earlier and use all the slots you have instead of sitting around waiting for the full type checking of the bodies (which other crates largely don’t care about). Something like 40% wall time speed up, maybe 10% to 15% if you have the parallel frontend on.
- adamch
I'm glad to see the donations from big companies to open source maintainers are making measurable difference to the Rust experience. Telling these companies that their employees spend 5% less time waiting for compilation might motivate future investment in people like Nick and the others mentioned.
- bryanlarsen
Really nice to see that the 5% speedup is despite making the borrow checker better, validating code that previously would have tripped it up.
Sometimes we really can have our cake and eat it too.
- s08148692
I finally gave in to the rust hype and built a new project in it (or my agent fleet did). Almost instant regret. My poor machine with just 2TB HDD and 24 cores was almost immediately crippled by agents each working in their own sandbox, each one building and compiling
Most projects my fleet works on are in other languages (TS, Go, Elixir) and can comfortably handle 10+ agents working in parallel, but not rust. I had to cap the fleet to 5 workers and build a dedicated resource monitor to step in and tidy up every time the disk almost filled up
That and general progress on building is far slower, with far more time spent building and testing than any other language I use.
Ended up rebuilding in Go, the perf gains weren't worth it
- slowin
I've moved from Rust to Go for most things because in the era of agents, being able to iterate quickly on a project is a huge advantage and Rust is way, way slower than Go for compilation. There are times when Rust is more appropriate, but for the vast majority of things Go is perfectly fine.
- Surac
Why is the compiler slow in the first place? I have no rust knowledge, how slow us slow, lets say in comparison to a c compiler?
What is the performance killer?
- maherbeg
I'm surprised the OpenAI Codex team doesn't donate like 10B tokens or something to the Rust team for performance
- hnp9j9qtda
Biggest win for me was splitting one fat crate into three, parallelism got real.