降低 Task.Factory.StartNew 线程的优先级

像下面这样的代码将启动一个新线程来完成这项工作。有什么方法可以控制该线程的优先级吗？

Task.Factory.StartNew(() => {
    // everything here will be executed in a new thread.
    // I want to set the priority of this thread to BelowNormal
});

正如其他人提到的，您需要指定一个自定义调度程序来配合您的任务。不幸的是没有合适的内置调度程序。

您可以使用 Glenn 链接到的 ParallelExtensionsExtras，但如果您想要一些可以直接粘贴到代码中的简单内容，请尝试以下操作。像这样使用：

Task.Factory.StartNew(() => {
    // everything here will be executed in a thread whose priority is BelowNormal
}, null, TaskCreationOptions.None, PriorityScheduler.BelowNormal);

代码：

public class PriorityScheduler : TaskScheduler
{
    public static PriorityScheduler AboveNormal = new PriorityScheduler(ThreadPriority.AboveNormal);
    public static PriorityScheduler BelowNormal = new PriorityScheduler(ThreadPriority.BelowNormal);
    public static PriorityScheduler Lowest = new PriorityScheduler(ThreadPriority.Lowest);

    private BlockingCollection<Task> _tasks = new BlockingCollection<Task>();
    private Thread[] _threads;
    private ThreadPriority _priority;
    private readonly int _maximumConcurrencyLevel = Math.Max(1, Environment.ProcessorCount);

    public PriorityScheduler(ThreadPriority priority)
    {
        _priority = priority;
    }

    public override int MaximumConcurrencyLevel
    {
        get { return _maximumConcurrencyLevel; }
    }

    protected override IEnumerable<Task> GetScheduledTasks()
    {
        return _tasks;
    }

    protected override void QueueTask(Task task)
    {
        _tasks.Add(task);

        if (_threads == null)
        {
            _threads = new Thread[_maximumConcurrencyLevel];
            for (int i = 0; i < _threads.Length; i++)
            {
                int local = i;
                _threads[i] = new Thread(() =>
                {
                    foreach (Task t in _tasks.GetConsumingEnumerable())
                        base.TryExecuteTask(t);
                });
                _threads[i].Name = $"PriorityScheduler: {i}";
                _threads[i].Priority = _priority;
                _threads[i].IsBackground = true;
                _threads[i].Start();
            }
        }
    }

    protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
    {
        return false; // we might not want to execute task that should schedule as high or low priority inline
    }
}

Notes:

• 工作线程都是后台线程，所以重要的任务不应该使用这个调度器来调度；仅那些在进程关闭时可以丢弃的内容
• 改编自Bnaya Eshet 的实现 https://web.archive.org/web/20150611052413/http://blogs.microsoft.co.il/bnaya/2011/01/29/how-to-schedule-task-on-different-thread-priority/
• 我并不完全理解每一个覆盖；只是同意 Bnaya 的选择MaximumConcurrencyLevel, GetScheduledTasks and TryExecuteTaskInline.