| name | rust100k-build-performance |
| description | Apply Matklad Rust100k build-time, inline, workspace, and generic-boundary guidance to eph. Use when changing Rust crate structure, public generic APIs, |
Rust100k Build Performance
Keep Rust build time and hot-path performance visible together. This skill covers Matklad's Inline In Rust, Large Rust Workspaces, and Fast Rust Builds posts, with eph's small-project conflict decisions documented in .agents/skills/readme.md.
Workflow
- Measure before tuning. For runtime changes use targeted command timings or smoke runs; for build changes use cargo timings, CI duration, or
cargo metadata plus targeted cargo commands.
- Treat
#[inline] as cross-crate body exposure, not a magic speed switch. In applications, add it reactively after profiling or for tiny public wrappers.
- Keep
#[inline(always)] rare and evidence-backed. Prefer #[cold] or #[inline(never)] for error/cold paths only when profiling or layout concerns justify it.
- For ergonomic generic public APIs, keep the generic wrapper thin and delegate immediately to a concrete implementation when compile-time bloat matters.
- For eph's single-crate shape, prefer
impl Trait or generics when they improve clarity or runtime performance. Split crates only when measurements or independent ownership boundaries justify it.
- If eph becomes a workspace, use a flat
crates/* layout, a virtual root manifest, folder names matching crate names, and a dedicated automation crate rather than scattered scripts.
- Run
cargo fmt --check, cargo test, and cargo clippy --all-targets -- -D warnings.
eph policy
- Keep
cargo fmt --check, cargo test, and cargo clippy --all-targets -- -D warnings as the ordinary gate.
- Keep clippy lint groups in the crate roots explicit so the policy is visible outside the Git hook and
Makefile.
- Do not add compile-time-heavy abstractions for hypothetical reuse.
- Prefer concrete data boundaries in shared internals, but allow
impl Trait where it improves current clarity or runtime performance.
- Treat release profile tuning as a measured change; document before/after latency and build-time impact.
Validation
cargo fmt --check
cargo clippy --all-targets -- -D warnings
cargo test -- --test-threads=1
Generic boundary and inline tradeoffs remain review rules. The crate-level lint attributes and CI commands are the executable policy.
Read references/article-notes.md for source notes and tool suggestions.
