rjprof

(Rust-Java profiler), similar to async-profiler.

Quick Start

# Build everything
make build

# Quick test with Hello World
make run-hello

# Test with Spring Boot application (builds and runs automatically)
make run-spring

# Profile your own JAR
make profile JAR=myapp.jar ARGS="--spring --mode user"

Project Structure

This project uses a Cargo workspace with two main components:

• librjprof/ - Core profiling library using JVMTI
• rjprof-cli/ - Command-line interface and tools
• examples/ - Sample applications for testing

Building

Simple Build (Recommended)

make build      # Release build
make dev        # Debug build (faster)
make install    # Build and copy binaries to bin/

Manual Build

cargo build --release --workspace

Requirements

• Rust (latest stable)
• Java Development Kit (JDK 8+) with JAVA_HOME set
• Maven (for Spring demo)
• Optional: flamegraph.pl or inferno-flamegraph for SVG generation

🔧 Usage

Basic Profiling

# Profile any JAR file
./target/release/rjprof --jar myapp.jar

# Profile with Spring filtering (removes framework noise)
./target/release/rjprof --jar myapp.jar --spring

# Focus on user code only
./target/release/rjprof --jar myapp.jar --mode user

# Filter by performance thresholds
./target/release/rjprof --jar myapp.jar --min-pct 0.5 --min-total 1ms

Advanced Options

# Custom package filtering
./target/release/rjprof --jar myapp.jar --exclude "java.*,org.apache.*" --include "com.mycompany.*"

# Different sorting and output options
./target/release/rjprof --jar myapp.jar --sort total --export json --no-color

# Verbose output with flamegraph generation
./target/release/rjprof --jar myapp.jar --verbose --generate-flamegraph

Profile Modes

• all - Profile everything (can be noisy)
• user - Focus on user code, exclude JDK/framework (default)
• hotspots - Only methods above performance thresholds
• allocation - Focus on allocation-heavy methods

Makefile Targets

Target	Description
make build	Build release version
make dev	Build debug version (faster)
make test	Run all tests
make run-hello	Quick test with Hello World
make run-spring	Test with Spring Boot demo
make flamegraph	Generate SVG from last run
make clean	Clean build artifacts
make help	Show all available targets

📊 Features

Smart Filtering

• Spring Boot optimized - Automatically filters common Spring/framework noise
• Custom package filtering - Include/exclude specific packages
• Performance thresholds - Hide methods below time/percentage limits
• Profile modes - Focus on different aspects of performance

Output Formats

• Colorized console output - Easy-to-read performance reports
• JSON export - Machine-readable data
• CSV export - Spreadsheet-compatible format
• Flamegraph generation - Visual performance analysis

Advanced Profiling

• Method entry/exit timing - Precise performance measurement
• Memory allocation tracking - Find allocation hotspots
• Call graph analysis - Understand call relationships
• Sampling support - Low-overhead profiling option

Examples

Profile Spring Boot Application

# Automatic: builds Spring demo and profiles it
make run-spring

# Manual: profile existing Spring JAR
./target/release/rjprof \
  --jar myspring.jar \
  --spring \
  --mode user \
  --min-pct 0.1 \
  --sort self \
  --generate-flamegraph

Custom Filtering for Microservice

./target/release/rjprof \
  --jar microservice.jar \
  --exclude "java.*,javax.*,org.springframework.*,org.apache.*" \
  --include "com.mycompany.*" \
  --mode hotspots \
  --min-total 5ms \
  --export json

Memory Allocation Analysis

./target/release/rjprof \
  --jar myapp.jar \
  --mode allocation \
  --sort calls \
  --min-self-time 100us

Flamegraph Generation

Generate visual flamegraphs for performance analysis:

# Run profiler with flamegraph generation
./target/release/rjprof --jar myapp.jar --generate-flamegraph

# Or generate from existing data
make flamegraph

Flamegraphs are saved to profiler_output/flamegraph.svg.

Development

Running Tests

make test                    # Run all tests
cargo test --workspace      # Manual test execution

Code Quality

make check                   # Check code without building
cargo clippy --workspace    # Run linter
cargo fmt --workspace       # Format code

Performance Tips

1. Use --mode user for most applications to focus on your code
2. Enable --spring for Spring Boot apps to reduce noise
3. Set thresholds with --min-pct and --min-total to hide trivial methods
4. Generate flamegraphs for visual analysis of performance bottlenecks
5. Export to JSON for integration with other analysis tools

Troubleshooting

Agent Not Found

# Manually specify agent path
./target/release/rjprof --jar myapp.jar --agent-path ./target/release/librjprof.dylib

JAVA_HOME Issues

# Ensure JAVA_HOME is set correctly
export JAVA_HOME=$(/usr/libexec/java_home)  # macOS
export JAVA_HOME=/usr/lib/jvm/default       # Linux

Build Issues

# Clean and rebuild
make clean
make build

# Check dependencies
cargo check --workspace

License

Licensed under either of:

• Apache License, Version 2.0
• MIT License

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