GoKawiilDeveloper builds buildprof tool to investigate Bun's Rust vs Zig compile speeds
A developer created an open-source tracing tool called buildprof that visualizes where time goes during software compilation on Linux, mapping every process and subprocess onto a single timeline. The project was sparked by a claim from Bun architect Jarred Sumner that Bun's new Rust build compiled over 5 times faster on Linux than its previous Zig build, a result the developer found suspicious given that the two builds used different link-time optimization settings—Full LTO for Zig versus ThinLTO for Rust.
GoKawiil's interpretation of the reporting above, not reported fact.
Build time comparisons between languages and toolchains are often used to argue for major rewrites, but such comparisons can be misleading if compiler flags and optimization settings aren't matched. A visualization tool like buildprof helps developers separate genuine language/tooling advantages from artifacts of configuration choices like LTO mode, which can make performance claims more rigorous and reproducible.
- buildprof is a new open-source tool that visually traces build processes to reveal bottlenecks like poor parallelism or redundant work.
- The tool was inspired by skepticism over a claim that Bun's Rust build was 5x faster than its Zig build on Linux.
- The comparison may have been skewed because the Zig build used slower Full LTO while the Rust build used faster ThinLTO.
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Published there as: “I made a build visualizer to understand Bun's compile times”
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