Async-profiler Native Mode Does Not Attach To An Embedded JVM

Mar 12, 2025 by ADMIN 62 views

Introduction

Async-profiler is a powerful tool for profiling and debugging applications, providing detailed insights into performance bottlenecks and code execution. However, when used in native mode on code that embeds a JVM (Java Virtual Machine), async-profiler may fail to attach to the embedded JVM, resulting in incomplete or inaccurate profiling data. This article explores the issue, its implications, and potential solutions.

Describe the Bug

When native async-profiler runs on code that embeds a JVM and calls from Rust/C/C++ into Java, async-profiler will not attach to the embedded JVM. This means that it won't have visibility into Java, and code that includes Java stack frames will appear to be .unknown. As a result, unwinding is broken, and you won't even see the Rust/C/C++ code that called into Java, only .unknown.

Causes of the Issue

The issue arises from the way async-profiler interacts with the JVM. When async-profiler is run in native mode, it uses a different mechanism to attach to the JVM compared to when it's run in Java mode. In native mode, async-profiler relies on the JVM's Attach API to attach to the JVM process. However, when the JVM is embedded within another process, the Attach API may not be available or may not work correctly, preventing async-profiler from attaching to the JVM.

Implications of the Issue

The failure of async-profiler to attach to the embedded JVM has significant implications for developers. Without accurate profiling data, it's challenging to identify performance bottlenecks and optimize code. The issue also affects code unwinding, making it difficult to diagnose issues and debug applications.

Expected vs. Actual Behavior

Expected Behavior

When running async-profiler in native mode on code that embeds a JVM, the expected behavior is that async-profiler should attach to the embedded JVM and provide accurate profiling data, including Java stack frames.

Actual Behavior

The actual behavior is that async-profiler fails to attach to the embedded JVM, resulting in incomplete or inaccurate profiling data. Code that includes Java stack frames appears as .unknown, and unwinding is broken.

Reproduction Steps

To reproduce the issue, follow these steps:

Create a project that embeds a JVM and calls from Rust/C/C++ into Java.
Run async-profiler in native mode on the project.
Observe that async-profiler fails to attach to the embedded JVM and provides incomplete or inaccurate profiling data.

Additional Information/Context

No additional information or context is available at this time.

Async-Profiler Version

The latest version of async-profiler is being used.

Environment Details

No environment details are available at this time.

Potential Solutions

Several potential solutions can address the issue:

Use Java Mode: Run async-profiler in Java mode instead of native mode. This may require modifying the project to use the Java API for async-profiler.
Modify the JVM Embedding: Modify the JVM embedding to use a different mechanism, such as the Process API, to attach to the JVM process.
Use a Different Profiler: Consider using a different profiler that supports native mode and can attach to the embedded JVM.

Conclusion

Introduction

In our previous article, we explored the issue of async-profiler native mode not attaching to an embedded JVM. This article provides a Q&A section to address common questions and concerns related to this issue.

Q: What is the cause of the issue?

A: The issue arises from the way async-profiler interacts with the JVM. When async-profiler is run in native mode, it uses a different mechanism to attach to the JVM compared to when it's run in Java mode. In native mode, async-profiler relies on the JVM's Attach API to attach to the JVM process. However, when the JVM is embedded within another process, the Attach API may not be available or may not work correctly, preventing async-profiler from attaching to the JVM.

Q: What are the implications of the issue?

A: The failure of async-profiler to attach to the embedded JVM has significant implications for developers. Without accurate profiling data, it's challenging to identify performance bottlenecks and optimize code. The issue also affects code unwinding, making it difficult to diagnose issues and debug applications.

Q: Can I use Java mode instead of native mode?

A: Yes, you can use Java mode instead of native mode. This may require modifying the project to use the Java API for async-profiler. However, this may also introduce additional complexity and overhead.

Q: How can I modify the JVM embedding to attach to the JVM process?

A: You can modify the JVM embedding to use a different mechanism, such as the Process API, to attach to the JVM process. However, this may require significant changes to the project and may not be feasible in all cases.

Q: Are there any other profilers that support native mode and can attach to the embedded JVM?

A: Yes, there are other profilers that support native mode and can attach to the embedded JVM. Some examples include:

VisualVM: A visual tool for profiling and debugging Java applications.
JProfiler: A commercial profiler for Java applications.
YourKit: A commercial profiler for Java applications.

Q: Can I use async-profiler in a multi-threaded environment?

A: Yes, async-profiler can be used in a multi-threaded environment. However, you may need to configure async-profiler to handle multi-threading correctly.

Q: How can I configure async-profiler to handle multi-threading?

A: You can configure async-profiler to handle multi-threading by using the --threads option to specify the number of threads to use. You can also use the --thread-priority option to specify the priority of each thread.

Q: Can I use async-profiler with a JVM that is not embedded within another process?

A: Yes, you can use async-profiler with a JVM that is not embedded within another process. In this case, async-profiler should be able to attach to the JVM process correctly.

Q: How can I troubleshoot issues with async-profiler?

A: You can troubleshoot issues with async-profiler by checking the following:

Async-profiler logs: Check the async-profiler logs for any error messages or warnings.
JVM logs: Check the JVM logs for any error messages or warnings.
System logs: Check the system logs for any error messages or warnings.

Conclusion

The failure of async-profiler to attach to the embedded JVM in native mode is a significant issue that affects developers working with code that embeds a JVM. By understanding the causes and implications of the issue, developers can explore potential solutions and workarounds to address the problem. This Q&A article provides additional information and guidance to help developers troubleshoot and resolve issues with async-profiler.