Can I keep threads alive and give them other workloads?

Question

Suppose I create threads with pthreads, is it possible to send them new things to work on after they have been initialized, so I don't waste resources in creating new threads? For instance, I create 3 threads, thread 2 signals completion and I send it another "task" without killing it and starting a new one. Thanks.

Answer 1

The usual, simple form is an ordinary (work) queue. In principle, you maintain a queue structure, perhaps as a linked list, protected by a mutex. Typically, condition variables are used by the main/producer threads to notify worker threads that new work is available, so they don't have to poll.

Some previous SO questions that may also be useful are:

• How To Use Condition Variable
• One producer, Two consumers and usage of pthread_cond_signal & pthread_mutex_lock
• pthread conditional variable

Answer 2

Yes, and that is what servers like Apache do to increase their performance. The design pattern is called the Thread pool pattern and there are various implementations (this one for example) using pthreads.

Of course, you might want to keep your implementation as simple as possible, depending on what your goals are.

Answer 3

Of course. For example, you can use producer-consumer pattern. Here is an example in C#, but it can be easily implemented in pthreads as well.

Answer 4

The search-keyword to your question is "thread pooling" or "thread pool". Using this terms you will find plenty information on this site and also in Google.