Performance Optimization Skill

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description: CLI performance optimization - startup time, memory usage, token savings benchmarking

Performance Optimization Skill

Systematic performance analysis and optimization for RTK CLI tool, focusing on **startup time (<10ms)**, **memory usage (<5MB)**, and **token savings (60-90%)**.

When to Use

• Automatically triggered: After filter changes, regex modifications, or dependency additions
• Manual invocation: When performance degradation suspected or before release
• Proactive: After any code change that could impact startup time or memory

RTK Performance Targets

Metric	Target	Verification Method	Failure Threshold
Startup time	<10ms	hyperfine 'rtk '	>15ms = blocker
Memory usage	<5MB resident	/usr/bin/time -l rtk (macOS)	>7MB = blocker
Token savings	60-90%	Tests with count_tokens()	<60% = blocker
Binary size	<5MB stripped	ls -lh target/release/rtk	>8MB = investigate

Performance Analysis Workflow

1. Establish Baseline

Before making any changes, capture current performance:

# Startup time baseline
hyperfine 'rtk git status' --warmup 3 --export-json /tmp/baseline_startup.json

# Memory usage baseline (macOS)
/usr/bin/time -l rtk git status 2>&1 | grep "maximum resident set size" > /tmp/baseline_memory.txt

# Memory usage baseline (Linux)
/usr/bin/time -v rtk git status 2>&1 | grep "Maximum resident set size" > /tmp/baseline_memory.txt

# Binary size baseline
ls -lh target/release/rtk | tee /tmp/baseline_binary_size.txt

2. Make Changes

Implement optimization or feature changes.

3. Rebuild and Measure

# Rebuild with optimizations
cargo build --release

# Measure startup time
hyperfine 'target/release/rtk git status' --warmup 3 --export-json /tmp/after_startup.json

# Measure memory usage
/usr/bin/time -l target/release/rtk git status 2>&1 | grep "maximum resident set size" > /tmp/after_memory.txt

# Check binary size
ls -lh target/release/rtk | tee /tmp/after_binary_size.txt

4. Compare Results

# Startup time comparison
hyperfine 'rtk git status' 'target/release/rtk git status' --warmup 3

# Example output:
#   Benchmark 1: rtk git status
#     Time (mean ± σ):       6.2 ms ±   0.3 ms    [User: 4.1 ms, System: 1.8 ms]
#   Benchmark 2: target/release/rtk git status
#     Time (mean ± σ):       7.8 ms ±   0.4 ms    [User: 5.2 ms, System: 2.1 ms]
#
#   Summary
#     'rtk git status' ran 1.26 times faster than 'target/release/rtk git status'

# Memory comparison
diff /tmp/baseline_memory.txt /tmp/after_memory.txt

# Binary size comparison
diff /tmp/baseline_binary_size.txt /tmp/after_binary_size.txt

5. Identify Regressions

**Startup time regression** (>15% increase or >2ms absolute):

# Profile with flamegraph
cargo install flamegraph
cargo flamegraph -- target/release/rtk git status

# Open flame