Demystifying Virtual Thread Performance: Unveiling the Truth Beyond the Buzz

Introduction

Virtual threads represent a groundbreaking approach to concurrent programming in Java, promising to simplify development while maintaining high performance. This article delves deep into virtual thread capabilities, comparing their performance against traditional blocking and reactive programming models.

Understanding Virtual Threads

Virtual threads, introduced in Java 19, offer a lightweight concurrency perfect that allows developers to write straightforward, sequential code without sacrificing scalability. Unlike platform threads, virtual threads are managed by the Java runtime, enabling more efficient resource utilization.

Benchmark Methodology

Test Environment

  • Platform: Quarkus Framework
  • Database: PostgreSQL
  • Application Type: Todo CRUD Application
  • Comparison Models:
    1. Imperative (Blocking)
    2. Reactive (Non-Blocking)
    3. Virtual Threads

Code Implementations

Imperative (Blocking) Service

In Quarkus requests, you can make methods and lessons with @Blocking annotation or non-stream return type

@Transactional

public List<Todo> getAll() { return Todo.listAll();}

Virtual Threads Service

It’s quite humble to make a blocking application into a virtual thread request. As you see in the following code snippets, you just essential to add a @RunOnVirtualThread annotation into the blocking service, getAll() method.

@Transactional

public List<Todo> getAll() { return Todo.listAll();}

Reactive (Non-Blocking) Service

Writing a reactive application must be a big challenge for Java developers when they need to comprehend the reactive programming perfect and the continuation and event stream handler implementation. Quarkus allows designers to implement both non-reactive and reactive requests in the same class because Quarkus remains built on reactive engines such as Netty and Vert.x. To make an asynchronous reactive claim in Quarkus, you can add a @NonBlocking explanation or set the arrival type with Uni or Multi in the SmallRye Mutiny plan as below the getAll() method.

public Uni<List<Todo>> getAll() {return Todo.listAll();}

To make the test result extra efficient and fair, we’ve tracked the Techempower guidelines such as conducting multiple situations, running on bare metal, and ampules on Kubernetes.

Here is the similar test scenario for the 3 claims (blocking, reactive, and virtual threads), as shown in Figure 1.

Fetch all rows from a DB (quotes)

Add one quote to the returned list

Sort the list

Reappearance the list as JSON

Performance test architecture

Performance Metrics Analysis

Response Time Comparison

Comparative analysis revealed:

  • Imperative: Moderate latency
  • Reactive: Low latency
  • Virtual Threads: Comparable to reactive, with more straightforward implementation

Throughput Evaluation

Virtual threads demonstrated:

  • High concurrent request handling
  • Minimal context-switching overhead
  • Efficient resource utilization

Resource Usage Insights

CPU Utilization

  • Virtual threads showed more balanced CPU consumption
  • Reduced thread management complexity
  • Lower context-switching penalties

Resident State Size (RSS)

  • Significantly reduced memory footprint
  • More efficient memory allocation
  • Lower container resource requirements

Practical Considerations for Production

When to Adopt Virtual Threads

  • High-concurrency workloads
  • I/O-bound applications
  • Microservices architectures
  • Applications requiring simple concurrent programming models

Potential Limitations

  • Not optimal for CPU-intensive tasks
  • Requires Java 19+ runtime
  • The learning curve for existing teams

Implementation Recommendations

  1. Gradually introduce virtual threads
  2. Benchmark against existing implementations
  3. Monitor application performance
  4. Consider incremental migration strategies

Conclusion

Demystifying Virtual Thread Performance: Unveiling the Truth Beyond the Buzz. Virtual threads represent a powerful abstraction for concurrent programming, offering a compelling balance between development simplicity and performance efficiency. While not a universal solution, they provide a promising approach for many modern Java applications.

As Java continues evolving, virtual threads will likely become a standard concurrency mechanism, revolutionizing how developers approach scalable application design.