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
threads;
for (std::size_t i = 0; i < gInitialThreadPoolSize; ++i) { boost::shared_ptrboost::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_ptrboost::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