Rust Performance

Measure speed, heap use, binary size, and build time on the host, Android, and iOS. The rust-hot-path skill, when it is installed, turns a named hotspot into a code change; the rust-observability skill owns tracing spans and structured timing in production.

Rules of engagement

1. Name one metric (items/s, MB/s, ms per pass, peak MB, bundle KB) and record a baseline before you change code. A change without a before and an after number is a guess.
2. Measure the build that ships; dev numbers do not transfer. On the host, profile the profiling profile below (release plus symbols). On a device, profile the ship profile with line tables and no strip.
3. Change one thing per measurement, on the same machine, power state, and device.
4. Fix the algorithm or the data structure before you tune build flags.

Build a profile that the profiler can read

A profile without symbols shows hex addresses and truncated stacks. A release build has no debug info (Cargo passes -C strip=debuginfo whenever debug is off, as of Cargo 1.99.1). Define this profile once in the workspace-root Cargo.toml: