# Rust Performance And Layout > Use for Rust performance work, allocation pressure, data layout, hot-path APIs, benchmarks, and when layout or copying choices affect runtime behaviour. Use when this capability is needed. - Skill: `tomevault-io/rust-performance-and-layout` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/rust-performance-and-layout` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/rust-performance-and-layout/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/rust-performance-and-layout --- # Rust Performance and Layout Use this when performance matters enough to justify design pressure. ## Working stance - Measure before changing shapes. - Fix the largest hot-path cost, not the most obvious micro-optimization. - Keep iterator pipelines lazy until you genuinely need a collection. - Reuse allocations and tighten data movement before reaching for cleverness. - Keep layout decisions explicit when they affect cache use or FFI. - Prefer simple code unless profiling proves it is the bottleneck. ## Decision surface | Pressure | First move | | --- | --- | | repeated allocation | reuse buffers, pre-size collections | | large enum or struct footprint | inspect layout, box rare large fields | | string and byte churn | borrow or use slices/bytes where lifetimes allow | | clone-heavy hot path | revisit ownership and API boundaries | | "faster" rewrite with no numbers | benchmark first | ## Red flags - benchmarking starts after the rewrite, - iterator chains collect into temporary `Vec`s only to be filtered or walked again, - hot loops build strings with repeated `format!()` calls, - index-based loops appear where iterators express the same walk clearly, - tiny local wins complicate the API surface, - hot-path code formats strings or allocates collections repeatedly, - data layout changes happen without measuring access patterns, - unsafe code is introduced before safe structural fixes are tried. Read [allocation-and-reuse.md](references/allocation-and-reuse.md), [data-layout.md](references/data-layout.md), [benchmark-discipline.md](references/benchmark-discipline.md), and [rigorous-benchmarking.md](references/rigorous-benchmarking.md) for the common forks. The last covers paired benchmarking (Tango), deterministic profiling (`iai-callgrind`), open-versus-closed load models, tail latency and goodput. --- > Source: [leynos/rust-skill](https://github.com/leynos/rust-skill) — distributed by [TomeVault](https://tomevault.io).