Simple guide to design work stealing thread pool in java

Work-stealing thread pools are a powerful concurrency pattern that can significantly improve the performance of parallel applications. In this post, we'll explore how to implement a work-stealing thread pool in Java from scratch. Checkout implementation here if you are interested in code.

What is Work Stealing?

Work stealing is a scheduling strategy used in parallel computing where idle processors "steal" work from busy processors. This helps balance the workload across all available threads and improves overall system performance.

Key Components

A work-stealing thread pool consists of several key components:

• Worker Threads: Each thread has its own work queue
• Work Queues: Double-ended queues for storing tasks
• Stealing Logic: Algorithm for redistributing work
• Task Submission: Mechanism for adding new tasks

Example

Here is how you can use the work stealing thread pool.

package net.nakshay.wstp;

import net.nakshay.wstp.internal.pool.WSTPFactory;
import net.nakshay.wstp.internal.service.WSTPService;
                        
import java.util.Random;
                    
public class Main {

    public static void main(String[] args) throws InterruptedException {
    WSTPService service = WSTPFactory.newThreadPool(5);
    for (int i = 0; i <1000;i++) {
        service.runJob(new Task(i));
    }

    }
}

class Task implements Runnable {
    private final int counter;

    Task(int counter) {
        this.counter = counter;
    }
    @Override
    public void run() {
        try {
            Thread.sleep(new Random().nextInt(1000));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("Running task "+ counter + " By Thread "+
            Thread.currentThread().getId());
    }
}
                    

Benefits

Work-stealing thread pools offer several advantages:

• Better load balancing across threads
• Reduced contention and synchronization overhead
• Improved cache locality
• Adaptive to varying task sizes

Conclusion

Work-stealing thread pools are an excellent choice for applications with irregular workloads or varying task sizes. They provide automatic load balancing and can significantly improve performance in parallel applications.

The implementation shown here is a simplified version. Production implementations like Java's ForkJoinPool include additional optimizations and features for better performance and reliability.