PThreads Programming

Chapter 2. Designing Threaded Programs

In this chapter:

• Suitable Tasks for Threading

• Models

• Buffering Data Between Threads

• Some Common Problems

• Performance

• Example: An ATM Server

• Example: A Matrix Multiplication Program

So far you’ve seen only a couple of Pthreads calls, but you know enough about the programming model to start considering real design issues. In this chapter we’ll examine a number of broad questions. How much work is worth the overhead of creating a thread? How can I subdivide my program into threads? What relationship do the threads have to the functions in my program?

To give us a sample application worth threading, we’ll introduce an application that will take us through most of the book: a server for automatic teller machines (ATMs). We’ll try out our design ideas on this server.

Suitable Tasks for Threading

To find the places in your program where you can use threads, you essentially must look for the properties we identified in Chapter 1: potential parallelism, overlapping I/O, asynchronous events, and real-time scheduling. Whenever a task has one or more of these properties, consider running it in a thread. You can identify a task that is suitable for threading by applying to it the following criteria:

• It is independent of other tasks.

  Does the task use separate resources from other tasks? Does its execution depend on the results of other tasks? Do other tasks depend on its results? We want to maximize concurrency and minimize the need for synchronization. The more tasks ...