Question

在Mono和MonoTouch下，我看到我打电话之间有大约500毫秒的延迟：

StartNew(Action<object> action, object state, CancellationToken cancellationToken, 
    TaskCreationOptions creationOptions, TaskScheduler scheduler);

当工作代码实际开始执行时。

我创建了一个测试来证明这一点：

public static class TestTaskFactory
{
    private class TaskInfo
    {
        public int Number;
    }

    private static int NUM_TASKS = 5;
    private static int NumFinished = 0;

    public static void Run()
    {
        for (int n = 1; n <= NUM_TASKS; n++)
        {
            Log("Starting task #" + n + " ...");
            var task_info = new TaskInfo { Number = n };
            var task = Task.Factory.StartNew(Worker, task_info, CancellationToken.None, TaskCreationOptions.None, TaskScheduler.Default);
            Thread.Sleep(0);
        }

        Log("Waiting for tasks to finish ...");
        while (NumFinished < NUM_TASKS)
        {
            Thread.Sleep(1);
        }

        Log("All done");
    }

    private static void Worker(object state)
    {
        var task_info = (TaskInfo)state;
        Log("Task #" + task_info.Number + " running");

        // Do something
        Thread.Sleep(2000);

        // Done
        ++NumFinished;
    }

    private static void Log(string msg)
    {
        Console.WriteLine(DateTime.Now.ToString("HH.mm.ss.fff") + ": Thread " + Thread.CurrentThread.ManagedThreadId + ": " + msg);
    }
}

Mac下Mono下的输出：

16.57.31.420: Thread 1: Starting task #1 ...
16.57.31.508: Thread 1: Starting task #2 ...
16.57.31.508: Thread 1: Starting task #3 ...
16.57.31.508: Thread 1: Starting task #4 ...
16.57.31.508: Thread 1: Starting task #5 ...
16.57.31.508: Thread 1: Waiting for tasks to finish ...
16.57.31.510: Thread 5: Task #1 running
16.57.32.009: Thread 6: Task #2 running <-- Approx 500 msec later
16.57.32.511: Thread 7: Task #3 running <-- Approx 500 msec later
16.57.33.012: Thread 8: Task #4 running <-- Approx 500 msec later
16.57.33.513: Thread 9: Task #5 running <-- Approx 500 msec later
16.57.35.515: Thread 1: All done

就好像Mono想要在产生一个新线程之前等待500毫秒来重用现有线程。如果我将工作时间减少到500毫秒以下，则延迟会减少。例如，将工作线程Thread.Sleep（2000）更改为Thread.Sleep（50）：

...
17.13.20.262: Thread 5: Task #1 running
17.13.20.314: Thread 5: Task #2 running <-- approx 50 msec later
17.13.20.365: Thread 5: Task #3 running <-- approx 50 msec later
17.13.20.416: Thread 5: Task #4 running <-- approx 50 msec later
17.13.20.466: Thread 5: Task #5 running <-- approx 50 msec later

但是在MS Framework 4.0下，在工作代码启动之前没有大延迟：

...
17.05.42.238: Thread 9: Waiting for tasks to finish ...
17.05.42.256: Thread 11: Task #1 running
17.05.42.256: Thread 12: Task #3 running <-- little delay
17.05.42.256: Thread 13: Task #4 running <-- little delay
17.05.42.257: Thread 10: Task #2 running <-- little delay
17.05.43.264: Thread 14: Task #5 running <-- little delay

在我提交关于Mono的错误报告之前，我想要理智地检查我是否错过了我需要在Mono上进行的一些调整或使用Task.Factory错误。我实际上在我的真实应用程序中使用了最大并发调度程序。

所以我的问题：这是Mono / MonoTouch中的错误吗？

更新：我已经从使用Mono *下的ThreadPool切换到Ami Bar的智能线程池（github; Code Project article）。 GSerjo的Extended Thread Pool看起来也不错，但是我在移动设备上试图避免使用很多依赖项。我在Xamarim thread写了一些简单的测试。我可能错过了其他100个线程池实现，但到目前为止我对SmartThreadPool感到满意。使用WINDOWS_PHONE模式在MonoTouch下编译。

Answer 1

所以我的问题：这是Mono / MonoTouch中的错误吗？

不一定。我怀疑它只是线程池不愿意每500毫秒启动一个以上的新线程。请注意，您会立即看到第一个任务启动。只有在那之后你才会看到延迟。

如果你在.NET 4.5上使用更多的任务，你会看到类似的东西，除了每秒开始的“大块”线程。

您可能会发现调用ThreadPool.SetMinThreads会有所帮助，假设在MonoTouch中可用。

Task.Factory.StartNew（）在Mono / MonoTouch下延迟

1 个答案: