高CPU调试（一）

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本文通过分析三个不同时间点的dump文件，详细记录了使用Windbg排查.NET应用程序中线程0持续高CPU占用的原因，并逐步定位到具体代码位置。

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        static void Main(string[] args)
        {
            Console.Clear();
            Console.WriteLine("到命令行下，切换到windbg目录，执行adplus -hang -pn highcpu.exe -o c:\\dumps");
            Console.WriteLine("如果要停止，按Ctrl+C结束程序");
            Console.WriteLine("====================================================");
            
            while (true)
            {
                Console.SetCursorPosition(0, 3);
                Console.Write(DateTime.Now.Ticks.ToString());
            }

            Console.ReadKey();
        }

dmp：

第一个Dump:
0:000> .load clr20\sos.dll
0:000> !runaway
 User Mode Time
  Thread       Time
   0:334       0 days 0:00:00.468
   3:dc8       0 days 0:00:00.000
   2:14d0      0 days 0:00:00.000
   1:750       0 days 0:00:00.000

第二个Dump:
0:000> .load clr20\sos.dll
0:000> !runaway
 User Mode Time
  Thread       Time
   0:334       0 days 0:00:08.221
   3:dc8       0 days 0:00:00.000
   2:14d0      0 days 0:00:00.000
   1:750       0 days 0:00:00.000

第三个Dump:
0:000> .load clr20\sos.dll
0:000> !runaway
 User Mode Time
  Thread       Time
   0:334       0 days 0:00:11.559
   3:dc8       0 days 0:00:00.000
   2:14d0      0 days 0:00:00.000
   1:750       0 days 0:00:00.000

从上面的输出可以看到，线程0的CPU时间不断增加，CPU高占用很可能是由于线程0正在执行的代码有问题造成的。

　　可以用!clrstack命令查看一下当前的调用堆栈以及其上的局部变量和值。

　　当执行!clrstack时，报出了如下提示：

0:000> !clrstack
Failed to find runtime DLL (mscorwks.dll), 0x80004005
Extension commands need mscorwks.dll in order to have something to do.

这不是我想要的，加载mscorwks失败。后来经过调试发现，原来是第一步就.load时就错了，因为我的那段代码用的是vs2010。所以应该加载.net frameword 4.0。

　　所以，最初应该执行的.load C:/WINDOWS/Microsoft.NET/Framework/v4.0.30319/sos.dll

　　然后在执行!clrstack

　　第三个Dump

0:000> !clrstack
*** ERROR: Symbol file could not be found.  Defaulted to export symbols for clr.dll - 
PDB symbol for clr.dll not loaded
OS Thread Id: 0x334 (0)
Child SP       IP Call Site
001cf2b8 779e70f4 [InlinedCallFrame: 001cf2b8] 
001cf2b4 6a14672e *** WARNING: Unable to verify checksum for mscorlib.ni.dll
DomainNeutralILStubClass.IL_STUB_PInvoke(IntPtr, COORD)
001cf2b8 6a1b6cfd [InlinedCallFrame: 001cf2b8] Microsoft.Win32.Win32Native.SetConsoleCursorPosition(IntPtr, COORD)
001cf2ec 6a1b6cfd System.Console.SetCursorPosition(Int32, Int32)
001cf324 005500bb *** WARNING: Unable to verify checksum for ConsoleApplication3.exe
ConsoleApplication3.Program.Main(System.String[]) [C:\Users\ChenZhuo\documents\visual studio 2010\Projects\ConsoleApplication3\ConsoleApplication3\Program.cs @ 22]
001cf4dc 70a33e22 [GCFrame: 001cf4dc]

第二个Dump

0:000> !clrstack
*** ERROR: Symbol file could not be found.  Defaulted to export symbols for clr.dll - 
PDB symbol for clr.dll not loaded
OS Thread Id: 0x334 (0)
Child SP       IP Call Site
001cf2b8 779e70f4 [InlinedCallFrame: 001cf2b8] 
001cf2b4 6a14672e *** WARNING: Unable to verify checksum for mscorlib.ni.dll
DomainNeutralILStubClass.IL_STUB_PInvoke(IntPtr, COORD)
001cf2b8 6a1b6cfd [InlinedCallFrame: 001cf2b8] Microsoft.Win32.Win32Native.SetConsoleCursorPosition(IntPtr, COORD)
001cf2ec 6a1b6cfd System.Console.SetCursorPosition(Int32, Int32)
001cf324 005500bb *** WARNING: Unable to verify checksum for ConsoleApplication3.exe
ConsoleApplication3.Program.Main(System.String[]) [C:\Users\ChenZhuo\documents\visual studio 2010\Projects\ConsoleApplication3\ConsoleApplication3\Program.cs @ 22]
001cf4dc 70a33e22 [GCFrame: 001cf4dc]

第一个Dump：

0:000> !clrstack
*** ERROR: Symbol file could not be found.  Defaulted to export symbols for clr.dll - 
PDB symbol for clr.dll not loaded
OS Thread Id: 0x334 (0)
Child SP       IP Call Site
001cf2b8 779e70f4 [InlinedCallFrame: 001cf2b8] 
001cf2b4 6a14672e *** WARNING: Unable to verify checksum for mscorlib.ni.dll
DomainNeutralILStubClass.IL_STUB_PInvoke(IntPtr, COORD)
001cf2b8 6a1b6cfd [InlinedCallFrame: 001cf2b8] Microsoft.Win32.Win32Native.SetConsoleCursorPosition(IntPtr, COORD)
001cf2ec 6a1b6cfd System.Console.SetCursorPosition(Int32, Int32)
001cf324 005500bb *** WARNING: Unable to verify checksum for ConsoleApplication3.exe
ConsoleApplication3.Program.Main(System.String[]) [C:\Users\ChenZhuo\documents\visual studio 2010\Projects\ConsoleApplication3\ConsoleApplication3\Program.cs @ 22]
001cf4dc 70a33e22 [GCFrame: 001cf4dc]

出问题的代码已可以看得到，就在Main方法里。