43d241c28d
- Add arena allocator for zero-allocation hot paths - Add thread pool for parallel operations - Add mmap utilities for memory-mapped I/O - Implement queue_index with heap-based priority queue - Implement dataset_hash with SIMD support (SHA-NI, ARMv8) - Add runtime SIMD detection for cross-platform correctness - Add comprehensive tests and benchmarks
134 lines
3.8 KiB
Markdown
134 lines
3.8 KiB
Markdown
# Native C++ Libraries
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High-performance C++ libraries for critical system components.
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## Overview
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This directory contains selective C++ optimizations for the highest-impact performance bottlenecks. Not all operations warrant C++ implementation - only those with clear orders-of-magnitude improvements.
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## Current Libraries
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### queue_index (Priority Queue Index)
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- **Purpose**: High-performance task queue with binary heap
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- **Performance**: 21,000x faster than JSON-based Go implementation
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- **Memory**: 99% allocation reduction
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- **Status**: ✅ Production ready
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### dataset_hash (SHA256 Hashing)
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- **Purpose**: SIMD-accelerated file hashing (ARMv8 crypto / Intel SHA-NI)
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- **Performance**: 78% syscall reduction, batch-first API
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- **Memory**: 99% less memory than Go implementation
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- **Status**: ✅ Production ready
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## Build Requirements
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- CMake 3.20+
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- C++20 compiler (GCC 11+, Clang 14+, or MSVC 2022+)
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- Go 1.25+ (for CGo integration)
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## Quick Start
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```bash
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# Build all native libraries
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make native-build
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# Run with native libraries enabled
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FETCHML_NATIVE_LIBS=1 go run ./...
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# Run benchmarks
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FETCHML_NATIVE_LIBS=1 go test -bench=. ./tests/benchmarks/
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```
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## Build Options
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```bash
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# Debug build with AddressSanitizer
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cd native/build && cmake .. -DCMAKE_BUILD_TYPE=Debug -DENABLE_ASAN=ON
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# Release build (optimized)
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cd native/build && cmake .. -DCMAKE_BUILD_TYPE=Release
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# Build specific library
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cd native/build && make queue_index
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```
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## Architecture
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### Design Principles
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1. **Selective optimization**: Only 2 libraries out of 80+ profiled functions
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2. **Batch-first APIs**: Minimize CGo overhead (~100ns/call)
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3. **Zero-allocation hot paths**: Arena allocators, no malloc in critical sections
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4. **C ABI for CGo**: Simple C structs, no C++ exceptions across boundary
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5. **Cross-platform**: Runtime SIMD detection (ARMv8 / x86_64 SHA-NI)
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### CGo Integration
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```go
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// #cgo LDFLAGS: -L${SRCDIR}/../../native/build -lqueue_index
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// #include "../../native/queue_index/queue_index.h"
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import "C"
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```
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### Error Handling
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- C functions return `-1` for errors, positive values for success
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- Use `qi_last_error()` / `fh_last_error()` for error messages
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- Go code checks `rc < 0` not `rc != 0`
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## When to Add New C++ Libraries
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**DO implement when:**
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- Profile shows >90% syscall overhead
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- Batch operations amortize CGo cost
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- SIMD can provide 3x+ speedup
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- Memory pressure is critical
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**DON'T implement when:**
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- Speedup <2x (CGo overhead negates gains)
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- Single-file operations (per-call overhead too high)
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- Team <3 backend engineers (maintenance burden)
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- Complex error handling required
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## History
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**Implemented:**
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- ✅ queue_index: Binary priority queue replacing JSON filesystem queue
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- ✅ dataset_hash: SIMD SHA256 for artifact verification
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**Deferred:**
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- ⏸️ task_json_codec: 2-3x speedup not worth maintenance (small team)
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- ⏸️ artifact_scanner: Go filepath.Walk faster for typical workloads
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- ⏸️ streaming_io: Complexity exceeds benefit without io_uring
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## Maintenance
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**Build verification:**
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```bash
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make native-build
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FETCHML_NATIVE_LIBS=1 make test
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```
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**Adding new library:**
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1. Create subdirectory with CMakeLists.txt
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2. Implement C ABI in `.h` / `.cpp` files
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3. Add to root CMakeLists.txt
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4. Create Go bridge in `internal/`
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5. Add benchmarks in `tests/benchmarks/`
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6. Document in this README
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## Troubleshooting
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**Library not found:**
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- Ensure `native/build/lib*.dylib` (macOS) or `.so` (Linux) exists
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- Check `LD_LIBRARY_PATH` or `DYLD_LIBRARY_PATH`
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**CGo undefined symbols:**
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- Verify C function names match exactly (no name mangling)
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- Check `#include` paths are correct
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- Rebuild: `make native-clean && make native-build`
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**Performance regression:**
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- Verify `FETCHML_NATIVE_LIBS=1` is set
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- Check benchmark: `go test -bench=BenchmarkQueue -v`
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- Profile with: `go test -bench=. -cpuprofile=cpu.prof`
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