# Generate Java flame graphs using async-profiler

## In this learning path

- [Introduction](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/)
- [Set up Tomcat benchmark environment](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/1_setup/)
- [Generate Java flame graphs using async-profiler](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/2_async-profiler/)
- [Generate Java flame graphs using a Java agent](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/3_agent/)
- [Next Steps](https://learn.arm.com/learning-paths/servers-and-cloud-computing/java-perf-flamegraph/_next-steps/)

## Overview
[Async-profiler](https://github.com/async-profiler/async-profiler) is a low-overhead sampling profiler for JVM applications. It can capture CPU usage, memory allocations, and lock events to generate flame graphs and detailed stack traces.

This tool is well-suited for production environments due to its minimal runtime impact. In this section, you’ll install and run `async-profiler` to analyze performance on your Tomcat instance under benchmark load.

> **Note**  
> Install and run `async-profiler` on the same Arm-based Linux machine where Tomcat is running to ensure accurate profiling.

## Install async-profiler
Download and extract the latest release:

```
wget -c https://github.com/async-profiler/async-profiler/releases/download/v4.0/async-profiler-4.0-linux-arm64.tar.gz
tar xzf async-profiler-4.0-linux-arm64.tar.gz
```

## Run the profiler
Navigate to the profiler binary directory:

```
cd async-profiler-4.0-linux-arm64/bin
```

Run async-profiler against the Tomcat process:

```
./asprof -d 10 -f profile.html $(jps | awk /Bootstrap/'{print $1}')
```

Alternatively, if you already know the process ID (PID):

```
./asprof -d 10 -f profile.html ${tomcat_process_id}
```

- `-d 10` sets the profiling duration to 10 seconds
- `-f profile.html` specifies the output file

## View the flame graph
Open the generated `profile.html` file in a browser to view your Java flame graph:

![Java flame graph built using async-profiler](https://example.com/path/to/lp-flamegraph-async.webp)  
*Java flame graph built using async-profiler*