rust-performancelisted

# Rust Performance Optimize from evidence. Define the user-visible metric, reproduce the workload, establish a stable baseline, profile the dominant cost, change one cause, and prove both correctness and improvement. ## Quick Reference Optimization priority — always fix the highest rung first: ```text 1. Algorithm choice 10x-1000x biggest impact 2. Data structure 2x-10x 3. Reduce allocations 2x-5x 4. Cache locality 1.5x-3x 5. SIMD / parallelism 2x-8x ``` Pick the measurement layer before touching code: | Question | Tool | |---|---| | Is a pure operation faster? | Criterion / Divan microbenchmark | | Did instruction-level cost change? | iai-callgrind (deterministic, CI-friendly) | | Where is CPU time spent? | samply, `cargo flamegraph`, perf, Instruments | | Where are allocations retained? | DHAT, heaptrack, allocator metrics | | Why is the binary large? | `cargo bloat`, feature inspection | | What drives compile time? | `cargo build --timings`, `cargo llvm-lines` | | Does the service meet its SLO? | representative load test + observability | A microbenchmark never proves end-to-end latency, overload behavior, or memory bounds. Match the tool to the question. ## Workflow ### 1. Define the performance contract Record workload, dataset, inputs, concurrency, platform, CPU/memory limits, toolchain, target, features, allocator, build profile, warm-up, cache state, and the success metric. Separate throughput from p50/p95/p99 latency, and steady state f