Edouard Vanbelle
83 lines
2.2 KiB
Markdown
83 lines
2.2 KiB
Markdown
# 05 - LTO Optimizations
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OxiCloud uses Link Time Optimization (LTO) to improve runtime performance. LTO allows the compiler to optimize across module boundaries during linking -- better inlining, dead code elimination, and more efficient binaries.
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---
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## Implemented Optimizations
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### Release Profile
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```toml
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[profile.release]
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lto = "fat" # Full cross-module optimization
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codegen-units = 1 # Maximum optimization but slower compile time
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opt-level = 3 # Maximum optimization level
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panic = "abort" # Smaller binary size by removing panic unwinding
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strip = true # Removes debug symbols for smaller binary
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```
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### Development Profile
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```toml
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[profile.dev]
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opt-level = 1 # Light optimization for faster build time
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debug = true # Keep debug information for development
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```
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### Benchmark Profile
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```toml
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[profile.bench]
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lto = "fat" # Full optimization for benchmarks
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codegen-units = 1 # Maximum optimization
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opt-level = 3 # Maximum optimization level
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```
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---
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## Performance Effects
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1. **Smaller binary size** -- unused code and metadata removed
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2. **Faster execution** -- better inlining and code optimizations
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3. **Reduced memory usage** -- more efficient code layout
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---
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## LTO Options
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- **fat**: Full LTO across all crate boundaries. Maximum optimization, longest compile time.
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- **thin**: Faster LTO that trades some optimization for compile speed. Good for development.
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- **off**: No cross-module optimization.
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---
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## Build Time Impact
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LTO increases compilation time. The tradeoff:
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- Development builds: minimal LTO (`opt-level = 1`) for faster iteration
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- Release builds: full LTO for maximum runtime performance
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- Benchmark builds: full LTO to measure actual optimized performance
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---
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## Measuring Impact
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```bash
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# Run benchmarks with all optimizations
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cargo bench
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# Compare with non-optimized build (remove for comparison only)
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RUSTFLAGS="-C lto=off" cargo bench
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```
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---
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## When to Adjust
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Consider changing these settings if:
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1. You need faster compile times during development
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2. You're experiencing unexpected runtime behavior
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3. You want to experiment with optimization vs. binary size tradeoffs
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The defaults work well for most cases.
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