AgentSkillsCN

rust-wasm-optimization

针对WebAssembly编译和运行时性能优化Rust代码。在构建WASM应用程序、优化二进制大小或提升WASM运行时性能时使用。

SKILL.md
--- frontmatter
name: rust-wasm-optimization
description: Optimize Rust code for WebAssembly compilation and runtime performance. Use when building WASM applications, optimizing binary size, or improving WASM runtime performance.

Rust WASM Optimization

Overview

This skill covers optimization techniques for Rust code compiled to WebAssembly, including binary size reduction, runtime performance improvements, and build configuration.

Build Configuration

Cargo.toml Profiles

toml
[profile.release]
opt-level = "z"        # Optimize for size
lto = "thin"           # Thin LTO for faster builds
codegen-units = 1      # Single codegen unit for better optimization
panic = "abort"        # Smaller binary (no unwinding)

[profile.wasm-release]
inherits = "release"
strip = false          # WASM doesn't support strip the same way

[profile.wasm-dev]
inherits = "dev"
opt-level = 1          # Light optimization for dev
incremental = true
codegen-units = 16     # Faster compilation

Linker Optimization

toml
# .cargo/config.toml
[target.wasm32-unknown-unknown]
# wasm-ld is already optimized for WASM

Binary Size Optimization

Minimize Dependencies

toml
# Only include needed features
[dependencies]
dioxus = { version = "0.6", features = ["web"] }  # Not ["web", "router", "ssr"]
serde = { version = "1.0", features = ["derive"] }  # Minimal features

Avoid Large Types

rust
// ❌ Don't store large binary data
struct Reminder {
    image_data: Vec<u8>,  // Large allocation
}

// ✅ Store URL instead
struct Reminder {
    image_url: String,  // Small string
}

Use Compact Types

rust
// Use small types when possible
struct Reminder {
    id: String,        // Required
    title: String,     // Required
    completed: bool,   // 1 byte
    // Avoid large types unless needed
}

Runtime Performance

Avoid Unnecessary Allocations

rust
// ❌ Unnecessary clone
for reminder in reminders.clone() {
    process(reminder);
}

// ✅ Use reference
for reminder in reminders.iter() {
    process(reminder);
}

Minimize Serialization Overhead

rust
// Use compact JSON field names
#[derive(Serialize, Deserialize)]
struct Reminder {
    #[serde(rename = "id")]
    id: String,
    #[serde(rename = "t")]
    title: String,  // Shorter name = smaller JSON
}

Efficient String Handling

rust
// ✅ Use &str when possible
fn format_title(title: &str) -> String {
    format!("Title: {}", title)
}

// ✅ Pre-allocate capacity
let mut buffer = String::with_capacity(100);
buffer.push_str("prefix");

Memory Management

Let Rust Manage Memory

rust
// Rust automatically manages memory
let reminders = load_reminders();  // Dropped when out of scope

Avoid Smart Pointers Unless Needed

rust
// ❌ Usually not needed in Dioxus
use std::rc::Rc;
let shared = Rc::new(data);

// ✅ Dioxus handles sharing via signals
let mut data = use_signal(|| value);

Build Optimization

Parallel Compilation

bash
# Use all CPU cores
export CARGO_BUILD_JOBS=$(nproc)
dx build --release

Incremental Compilation

toml
[profile.dev]
incremental = true  # Faster rebuilds

Codegen Units

toml
[profile.wasm-dev]
codegen-units = 16  # More units = faster compilation, slightly larger binary

[profile.release]
codegen-units = 1   # Single unit = better optimization, smaller binary

WASM-Specific Considerations

Panic Strategy

toml
[profile.release]
panic = "abort"  # Smaller binary, no unwinding code

LTO Configuration

toml
[profile.release]
lto = "thin"  # Faster builds than "fat", still good optimization

Strip Configuration

toml
[profile.wasm-release]
strip = false  # WASM doesn't support strip the same way as native binaries

Performance Profiling

Measure Binary Size

bash
# Check WASM file size
ls -lh target/wasm32-unknown-unknown/release/*.wasm

# Use wasm-opt for further optimization
wasm-opt -Oz target/.../app.wasm -o app.optimized.wasm

Runtime Profiling

rust
// Use web_sys::console for timing
use web_sys::console;

let start = js_sys::Date::now();
// ... operation ...
let duration = js_sys::Date::now() - start;
console::log_1(&format!("Operation took: {}ms", duration).into());

Best Practices

DO:

  • •✅ Use opt-level = "z" for size optimization
  • •✅ Use lto = "thin" for balance of size and build time
  • •✅ Minimize dependencies and features
  • •✅ Use references instead of clones
  • •✅ Pre-allocate collections when size is known
  • •✅ Use compact JSON field names

DON'T:

  • •❌ Don't include unused features in dependencies
  • •❌ Don't store large binary data in structs
  • •❌ Don't clone unnecessarily
  • •❌ Don't use strip = true for WASM (not supported)
  • •❌ Don't use lto = true (use "thin" instead)

Resources