GetThreadTimes为什么返回

Question

我试图测量线程中用于进度报告目的的时间，但是我从GetThreadTimes系统调用中得到了非常奇怪的结果。考虑下面的程序（在VS 2013编译，针对.NET 4.5）：

using System; 
using System.Diagnostics; 
using System.Runtime.InteropServices; 
using System.Threading; 

namespace ThreadTimingTest 
{ 
    class Program 
    { 
     static Stopwatch _wallClockTimer; 

     static System.Timers.Timer _timer = new System.Timers.Timer(); 

     private static Thread _thread; 
     private static IntPtr _threadHandle; 

     static void Main(string[] args) 
     { 
      _timer = new System.Timers.Timer(); 
      _timer.Elapsed += (s, e) => 
      { 
       System.Runtime.InteropServices.ComTypes.FILETIME start, end, rawKernelTime, rawUserTime; 

       GetThreadTimes(_threadHandle, out start, out end, out rawKernelTime, out rawUserTime); 

       //ref: http://stackoverflow.com/a/6083846 
       ulong uLow = (ulong)rawKernelTime.dwLowDateTime; 
       ulong uHigh = (uint)rawKernelTime.dwHighDateTime; 
       uHigh = uHigh << 32; 
       long kernelTime = (long)(uHigh | uLow); 

       uLow = (ulong)rawUserTime.dwLowDateTime; 
       uHigh = (uint)rawUserTime.dwHighDateTime; 
       uHigh = uHigh << 32; 
       long userTime = (long)(uHigh | uLow); 

       Debug.WriteLine("Kernel time: " + kernelTime); 
       Debug.WriteLine("User time: " + userTime); 
       Debug.WriteLine("Combined raw execution time: " + (kernelTime + userTime)); 

       long elapsedMilliseconds = (kernelTime + userTime)/10000; //convert to milliseconds: raw timing unit is 100 nanoseconds 
       Debug.WriteLine("Elapsed thread time: " + elapsedMilliseconds + " milliseconds"); 

       Debug.WriteLine("Wall Clock Time: " + _wallClockTimer.ElapsedMilliseconds + " milliseconds"); 

      }; 

      _timer.Interval = 1000; 

      _wallClockTimer = new Stopwatch(); 

      Debug.WriteLine("Starting..."); 
      RunTest(); 

      Debug.WriteLine("Ended."); 
     } 

     public static void RunTest() 
     { 
      _thread = 
       new Thread 
       (
        () => 
        { 
         _threadHandle = GetCurrentThread(); 
         Stopwatch sw = Stopwatch.StartNew(); 

         while (sw.ElapsedMilliseconds < 3000) 
         { 
          int i = 1 + 2; 
         } //do busy-work for 3 seconds 

         sw.Stop(); 
        } 
       ); 

      _timer.Start(); 

      _thread.Start();a 

      _wallClockTimer.Start(); 

      _thread.Join(); 
     } 

     [DllImport("kernel32.dll", SetLastError = true)] 
     static extern bool GetThreadTimes(IntPtr hThread, 
      out System.Runtime.InteropServices.ComTypes.FILETIME lpCreationTime, out System.Runtime.InteropServices.ComTypes.FILETIME lpExitTime, 
      out System.Runtime.InteropServices.ComTypes.FILETIME lpKernelTime, out System.Runtime.InteropServices.ComTypes.FILETIME lpUserTime); 

     [DllImport("kernel32.dll")] 
     private static extern IntPtr GetCurrentThread(); 
    } 
} 

我得到以下输出：

Starting... 
Kernel time: 0 
User time: 0 
Combined raw execution time: 0 
Elapsed thread time: 0 milliseconds 
Wall Clock Time: 1036 milliseconds 
Kernel time: 0 
User time: 0 
Combined raw execution time: 0 
Elapsed thread time: 0 milliseconds 
Wall Clock Time: 2036 milliseconds 
The thread '<No Name>' (0x191c) has exited with code 0 (0x0). 
Ended. 

我希望GetThreadTimes为螺纹次报告为零以外的东西：为什么零报告？

Answer 1

在根据Hans提供的链接对代码进行几个简单的修改后，将显示有效时间。

添加几个互操作的声明：

[DllImport("kernel32.dll", SetLastError = true)] 
[return: MarshalAs(UnmanagedType.Bool)] 
static extern bool DuplicateHandle(IntPtr hSourceProcessHandle, 
    IntPtr hSourceHandle, IntPtr hTargetProcessHandle, out IntPtr lpTargetHandle, 
    uint dwDesiredAccess, [MarshalAs(UnmanagedType.Bool)] bool bInheritHandle, uint dwOptions); 

[Flags] 
public enum DuplicateOptions : uint 
{ 
    DUPLICATE_CLOSE_SOURCE = (0x00000001), // Closes the source handle. This occurs regardless of any error status returned. 
    DUPLICATE_SAME_ACCESS = (0x00000002), // Ignores the dwDesiredAccess parameter. The duplicate handle has the same access as the source handle. 
} 

[DllImport("kernel32.dll")] 
static extern IntPtr GetCurrentProcess(); 

然后修改手柄如何分配：

//_threadHandle = GetCurrentThread();  <-- previous assignment 
IntPtr processHandle = GetCurrentProcess(); 
bool result = DuplicateHandle(processHandle, GetCurrentThread(), processHandle, out _threadHandle, 0, false, (uint) DuplicateOptions.DUPLICATE_SAME_ACCESS); 

产生以下结果：

Starting... 
Kernel time: 0 
User time: 10000000 
Combined raw execution time: 10000000 
Elapsed thread time: 1000 milliseconds 
Wall Clock Time: 1006 milliseconds 
Kernel time: 0 
User time: 20000000 
Combined raw execution time: 20000000 
Elapsed thread time: 2000 milliseconds 
Wall Clock Time: 2004 milliseconds 
Kernel time: 0 
User time: 30000000 
Combined raw execution time: 30000000 
Ended. 
Elapsed thread time: 3000 milliseconds 
Wall Clock Time: 3045 milliseconds 

编辑：

最近，我们付出了很大的努力来处理为给定系统创建的太多线程。假设你有一个四核处理器，并且有20多个线程都想运行。线程在启动，内核管理，内存（他们有自己的堆栈）等方面的成本相当高。与减少线程数量相比，系统实际上可能更慢（杂乱的上下文和调度）。所以在.NET中，创建了类似TPL的库（允许开发人员管理任务，而不是线程）。这使得CLR能够将适当的线程数量平衡到目标系统。但在你的情况下（你明确地创建一个托管线程），与本地线程几乎总是有1对1的关系。

希望这会有所帮助。