Question

I am trying to speed things by having one thread write to a linked list and another thread process the linked list.

For some reason if the method that writes to the linked list I make it into a task and the method that reads from the linked list a low priority thread the program finishes as a whole much faster. In other words I experiense fastests results when doing:

 Task.Factory.StartNew( AddItems );

 new Thread( startProcessingItems ) { Priority = ThreadPriority.Lowest }.Start();

 while(completed==false)
    Thread.Sleep(0);

Maybe because the first task is doing so much extra work than the other thread that’s why everything as a whole will finish faster if I set the second method a low priority.

Anyways now my question is The startProcessingItems runs with ThreadPriority = Lowest. How could I change it’s priority to highest? If I create a new Task in that method will it be running with low priority? Basically the startProcessingItems ends with a list and once it has that list I will like to start executing with highest priority.

Answer 1

This is not a good approach. First off, LinkedList<T> is not thread safe, so writing to it and reading from it in two threads will cause race conditions.

A better approach would be to use BlockingCollection<T>. This allows you to add items (producer thread) and read items (consumer thread) without worrying about thread safety, as it’s completely thread safe.

The reading thread can just call blockingCollection.GetConsumingEnumerable() in a foreach to get the elements, and the write thread just adds them. The reading thread will automatically block, so there’s no need to mess with priorities.

When the writing thread is “done”, you just call CompleteAdding, which will, in turn, allow the reading thread to finish automatically.