为什么我的线程池的线程不能同时完成

在主函数中，我编写了以下代码：

            ThreadPool.SetMaxThreads(200, 200);
        for (int i = 0; i < 100; i++)
        {
            ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadWhichWillCallSQL_test), i);
            Thread.Sleep(1);
        }

线程函数如下所示：

        static public void ThreadWhichWillCallSQL_test(Object o1)
    {
        Thread.Sleep(5000);
        Console.WriteLine(DateTime.Now.ToString()); 
        return;
    }

输出为：

    5/25/2017 2:00:01 PM
5/25/2017 2:00:01 PM
5/25/2017 2:00:01 PM
5/25/2017 2:00:01 PM
5/25/2017 2:00:02 PM
5/25/2017 2:00:03 PM
5/25/2017 2:00:04 PM
5/25/2017 2:00:05 PM
5/25/2017 2:00:05 PM
5/25/2017 2:00:06 PM
5/25/2017 2:00:06 PM
5/25/2017 2:00:06 PM
5/25/2017 2:00:06 PM
5/25/2017 2:00:07 PM
5/25/2017 2:00:07 PM
5/25/2017 2:00:08 PM
5/25/2017 2:00:08 PM
5/25/2017 2:00:09 PM
5/25/2017 2:00:09 PM
5/25/2017 2:00:10 PM
5/25/2017 2:00:10 PM
5/25/2017 2:00:10 PM
5/25/2017 2:00:11 PM
5/25/2017 2:00:11 PM
5/25/2017 2:00:11 PM
5/25/2017 2:00:11 PM
5/25/2017 2:00:12 PM
5/25/2017 2:00:12 PM
5/25/2017 2:00:12 PM
5/25/2017 2:00:13 PM
5/25/2017 2:00:13 PM
5/25/2017 2:00:13 PM
5/25/2017 2:00:14 PM
5/25/2017 2:00:14 PM
5/25/2017 2:00:14 PM
5/25/2017 2:00:15 PM
5/25/2017 2:00:15 PM
5/25/2017 2:00:15 PM
5/25/2017 2:00:15 PM
5/25/2017 2:00:16 PM
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5/25/2017 2:00:16 PM
5/25/2017 2:00:16 PM
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5/25/2017 2:00:17 PM
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5/25/2017 2:00:18 PM
5/25/2017 2:00:18 PM
5/25/2017 2:00:18 PM
5/25/2017 2:00:18 PM
5/25/2017 2:00:19 PM
5/25/2017 2:00:19 PM
5/25/2017 2:00:19 PM
5/25/2017 2:00:19 PM
5/25/2017 2:00:20 PM
5/25/2017 2:00:20 PM
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5/25/2017 2:00:22 PM
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5/25/2017 2:00:22 PM
5/25/2017 2:00:22 PM
5/25/2017 2:00:22 PM
5/25/2017 2:00:23 PM
5/25/2017 2:00:23 PM
5/25/2017 2:00:23 PM
5/25/2017 2:00:23 PM
5/25/2017 2:00:23 PM
5/25/2017 2:00:24 PM
5/25/2017 2:00:24 PM
5/25/2017 2:00:24 PM
5/25/2017 2:00:24 PM
5/25/2017 2:00:24 PM
5/25/2017 2:00:25 PM
5/25/2017 2:00:25 PM
5/25/2017 2:00:25 PM
5/25/2017 2:00:25 PM
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5/25/2017 2:00:25 PM
5/25/2017 2:00:26 PM
5/25/2017 2:00:26 PM
5/25/2017 2:00:26 PM
5/25/2017 2:00:26 PM
5/25/2017 2:00:27 PM
5/25/2017 2:00:27 PM
5/25/2017 2:00:27 PM
5/25/2017 2:00:27 PM
5/25/2017 2:00:27 PM
5/25/2017 2:00:27 PM
5/25/2017 2:00:28 PM
5/25/2017 2:00:28 PM
5/25/2017 2:00:28 PM
5/25/2017 2:00:28 PM
5/25/2017 2:00:28 PM

你可以注意到，整个过程所有线程的完成时间持续了将近28秒，据我了解，这100个线程可能不能同时完成，也不能有那么多时间相差。

我也设置了

ThreadPool.SetMaxThreads(200, 200);

并且只分配 100 个线程，所以不应该有任何线程等待其他人停止，对吧？

这是完整的代码

        using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;
    using System.Threading;
    namespace ThreadpoolDelay
    {
        class Program
        {
            static void Main(string[] args)
            {
                try
                {
                    ThreadPool.SetMaxThreads(200, 200);
                    for (int i = 0; i < 30; i++)
                    {
                        ThreadPool.QueueUserWorkItem(new WaitCallback(ThreadWhichWillCallSQL_test), i);
                    }
                }
                catch (Exception e)
                {
                    Console.WriteLine(e.ToString());
                }
                Console.WriteLine("nPress ENTER to continue...");
                Console.Read();
            }
            public static void ThreadWhichWillCallSQL_test(Object o1)
            {
                Thread.Sleep(5000);
                Console.WriteLine(DateTime.Now.ToString());
                return;
            }
        }
    }

在您的示例中，线程未同时启动。在 SetMaxThreads 之后添加以下调用

ThreadPool.SetMinThreads(200, 200);

这将使线程同时启动。这是关于ThreadPool线程创建机制的事情。我建议阅读 ThreadPool 文档以了解详细信息。

若要更正确地调试它，请更新ThreadWhichWillCallSQL_test方法以添加开始时间：

    static void ThreadWhichWillCallSQL_test(object o1)
    {
        Console.WriteLine("start:"  + DateTime.Now);
        Thread.Sleep(5000);
        Console.WriteLine("finish: " + DateTime.Now);
    }

好问题。

线程

拉取中线程的执行取决于许多因素，其中一个因素是 cpu核心 . 它把线程放在每个内核中运行，一旦完成，它就会放置另一个。

示例：如果有 4 核 CPU。它同时并行放置 4 个线程，然后在线程完成任务时放置下一个线程。机制是一些这样的，不完全是这样的。你也放了 5 秒的延迟(线程睡眠(，所以计算就像如果有 4 核：(30 线程/4 核(*5 有些不完全是这样的。

你也可以在那里看到更多信息：https://msdn.microsoft.com/en-us/library/3dasc8as(v=vs.80(.aspx

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