Add: windows mvp - transparent bugs not fixed
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DaZuo0122
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skills/m10-performance/SKILL.md
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skills/m10-performance/SKILL.md
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name: m10-performance
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description: "CRITICAL: Use for performance optimization. Triggers: performance, optimization, benchmark, profiling, flamegraph, criterion, slow, fast, allocation, cache, SIMD, make it faster, 性能优化, 基准测试"
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user-invocable: false
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---
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# Performance Optimization
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> **Layer 2: Design Choices**
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## Core Question
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**What's the bottleneck, and is optimization worth it?**
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Before optimizing:
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- Have you measured? (Don't guess)
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- What's the acceptable performance?
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- Will optimization add complexity?
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---
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## Performance Decision → Implementation
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| Goal | Design Choice | Implementation |
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|------|---------------|----------------|
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| Reduce allocations | Pre-allocate, reuse | `with_capacity`, object pools |
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| Improve cache | Contiguous data | `Vec`, `SmallVec` |
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| Parallelize | Data parallelism | `rayon`, threads |
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| Avoid copies | Zero-copy | References, `Cow<T>` |
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| Reduce indirection | Inline data | `smallvec`, arrays |
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---
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## Thinking Prompt
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Before optimizing:
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1. **Have you measured?**
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- Profile first → flamegraph, perf
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- Benchmark → criterion, cargo bench
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- Identify actual hotspots
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2. **What's the priority?**
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- Algorithm (10x-1000x improvement)
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- Data structure (2x-10x)
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- Allocation (2x-5x)
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- Cache (1.5x-3x)
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3. **What's the trade-off?**
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- Complexity vs speed
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- Memory vs CPU
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- Latency vs throughput
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---
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## Trace Up ↑
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To domain constraints (Layer 3):
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```
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"How fast does this need to be?"
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↑ Ask: What's the performance SLA?
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↑ Check: domain-* (latency requirements)
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↑ Check: Business requirements (acceptable response time)
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```
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| Question | Trace To | Ask |
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|----------|----------|-----|
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| Latency requirements | domain-* | What's acceptable response time? |
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| Throughput needs | domain-* | How many requests per second? |
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| Memory constraints | domain-* | What's the memory budget? |
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---
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## Trace Down ↓
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To implementation (Layer 1):
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```
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"Need to reduce allocations"
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↓ m01-ownership: Use references, avoid clone
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↓ m02-resource: Pre-allocate with_capacity
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"Need to parallelize"
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↓ m07-concurrency: Choose rayon or threads
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↓ m07-concurrency: Consider async for I/O-bound
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"Need cache efficiency"
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↓ Data layout: Prefer Vec over HashMap when possible
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↓ Access patterns: Sequential over random access
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```
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---
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## Quick Reference
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| Tool | Purpose |
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|------|---------|
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| `cargo bench` | Micro-benchmarks |
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| `criterion` | Statistical benchmarks |
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| `perf` / `flamegraph` | CPU profiling |
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| `heaptrack` | Allocation tracking |
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| `valgrind` / `cachegrind` | Cache analysis |
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## Optimization Priority
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```
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1. Algorithm choice (10x - 1000x)
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2. Data structure (2x - 10x)
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3. Allocation reduction (2x - 5x)
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4. Cache optimization (1.5x - 3x)
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5. SIMD/Parallelism (2x - 8x)
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```
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## Common Techniques
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| Technique | When | How |
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|-----------|------|-----|
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| Pre-allocation | Known size | `Vec::with_capacity(n)` |
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| Avoid cloning | Hot paths | Use references or `Cow<T>` |
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| Batch operations | Many small ops | Collect then process |
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| SmallVec | Usually small | `smallvec::SmallVec<[T; N]>` |
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| Inline buffers | Fixed-size data | Arrays over Vec |
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---
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## Common Mistakes
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| Mistake | Why Wrong | Better |
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|---------|-----------|--------|
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| Optimize without profiling | Wrong target | Profile first |
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| Benchmark in debug mode | Meaningless | Always `--release` |
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| Use LinkedList | Cache unfriendly | `Vec` or `VecDeque` |
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| Hidden `.clone()` | Unnecessary allocs | Use references |
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| Premature optimization | Wasted effort | Make it work first |
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---
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## Anti-Patterns
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| Anti-Pattern | Why Bad | Better |
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|--------------|---------|--------|
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| Clone to avoid lifetimes | Performance cost | Proper ownership |
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| Box everything | Indirection cost | Stack when possible |
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| HashMap for small sets | Overhead | Vec with linear search |
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| String concat in loop | O(n^2) | `String::with_capacity` or `format!` |
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---
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## Related Skills
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| When | See |
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|------|-----|
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| Reducing clones | m01-ownership |
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| Concurrency options | m07-concurrency |
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| Smart pointer choice | m02-resource |
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| Domain requirements | domain-* |
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