I am creating a simple task and timer thread pool using Boost.Asio. I am searching for the recommended way to dynamically add and remove threads to the thread pool. I don’t want to have to queue up tasks most of the time, only when the thread count gets very high (100s) queuing is ok, also I want for the thread count to go down to example 5 threads when there is no more work presented to the thread pool. This is because some of the tasks can take some time to complete and I don't want to hold off other tasks when computer resource are still available. Basically this is the solution I have in mind now. Given the following configuration values: gInitialThreadPoolSize = 4; gMaximumThreadPoolSize = 1024; gNumberOfThreadsDoingWork = 0; And 2 events: HANDLE moreWorkAvailable; HANDLE exit; Create a thread pool using this worker function: void ThreadWorkerFunction(boost::asio::io_service *io, boost::thread &thread) { for (;;) { HANDLE objects[] = { moreWorkAvailable, exit }; errorCode = WaitForMultipleObjects(objects) if (errorCode == WAIT_OBJECT_0) { // More work is available, lets start processing... gNumberOfThreadsDoingWork++; io->run(); gNumberOfThreadsDoingWork--; // When all work has been processed, go back to the original thread pool size if (threads.size() < gInitialThreadPoolSize ) { threads.remove(thread); break; } } else if (errorCode == WAIT_OBJECT_1) { threads.remove(thread); break; } } } This is now the thread pool is created: std::vector<boost::shared_ptr<boost::thread>
threads;
for (std::size_t i = 0; i < gInitialThreadPoolSize; ++i) { boost::shared_ptr<boost::thread> thread(new boost::thread( boost::bind(&ThreadWorkerFunction, &io, thread) )); threads.push_back(thread); } Next every time a task is inserted into the queue we check if all worker threads are busy, and in case they are busy, create a new thread if (threadsDoingWork == threads.size()) { boost::shared_ptr<boost::thread> thread(new boost::thread( boost::bind(&worker, &io) )); threads.push_back(thread); } SetEvent(moreWorkAvailable); Also in the ThreadWorkerFunction(...) function, after io->run() returns, we can check if more than N threads are idle and keep exiting until we get at minimum. I would appreciate if you can let me know if there is some better and more simpler way to achieve this than implementing this myself. I am new to Asio so I might have overlooked something. _________________________________________________________________ Hotmail: Trusted email with powerful SPAM protection. https://signup.live.com/signup.aspx?id=60969