Question

我想要做的是编写一个小程序，该程序连续生存计算特定进程在足够小的时间内经历的上下文切换的数量。我在软件“Process Explorer”中观察到了这个功能，所以我知道这绝对是可能的。

不幸的是，我很少知道如何开始编码，到目前为止还无法在网上找到任何有用的代码片段。因此，实现每个进程和每单位时间实时上下文切换计数的小工作示例对我来说非常有用。

Answer 1

这是一种方法 - 这将打印记事本的线程0使用的上下文切换量（您可以在CounterPathBuffer初始化中替换所需的任何进程和线程号）：

#include "stdafx.h"
#include <iostream>
#include <windows.h>
#include <stdio.h>
#include <conio.h>
#include <pdh.h>
#include <pdhmsg.h>

#pragma comment(lib, "pdh.lib")
using namespace std;
CONST ULONG SAMPLE_INTERVAL_MS    = 1000;
CONST PWSTR BROWSE_DIALOG_CAPTION = L"Select a counter to monitor.";

void wmain(void)
{
    PDH_STATUS Status;
    HQUERY Query = NULL;
    HCOUNTER Counter;
    PDH_FMT_COUNTERVALUE DisplayValue;
    DWORD CounterType;
    SYSTEMTIME SampleTime;
    PDH_BROWSE_DLG_CONFIG BrowseDlgData;
    WCHAR CounterPathBuffer[PDH_MAX_COUNTER_PATH] = L"\\\\ComputerNameGoesHere\\Thread(notepad/0)\\Context Switches/sec";


    //
    // Create a query.
    //

    Status = PdhOpenQuery(NULL, NULL, &Query);
    if (Status != ERROR_SUCCESS) 
    {
       wprintf(L"\nPdhOpenQuery failed with status 0x%x.", Status);
       goto Cleanup;
    }

    //
    // Initialize the browser dialog window settings.
    //



    ZeroMemory(&BrowseDlgData, sizeof(PDH_BROWSE_DLG_CONFIG));

    BrowseDlgData.bIncludeInstanceIndex = FALSE;
    BrowseDlgData.bSingleCounterPerAdd = TRUE;
    BrowseDlgData.bSingleCounterPerDialog = TRUE;
    BrowseDlgData.bLocalCountersOnly = FALSE;
    BrowseDlgData.bWildCardInstances = TRUE;
    BrowseDlgData.bHideDetailBox = TRUE;
    BrowseDlgData.bInitializePath = FALSE;
    BrowseDlgData.bDisableMachineSelection = FALSE;
    BrowseDlgData.bIncludeCostlyObjects = FALSE;
    BrowseDlgData.bShowObjectBrowser = FALSE;
    BrowseDlgData.hWndOwner = NULL;
    BrowseDlgData.szReturnPathBuffer = CounterPathBuffer;
    BrowseDlgData.cchReturnPathLength = PDH_MAX_COUNTER_PATH;
    BrowseDlgData.pCallBack = NULL;
    BrowseDlgData.dwCallBackArg = 0;
    BrowseDlgData.CallBackStatus = ERROR_SUCCESS;
    BrowseDlgData.dwDefaultDetailLevel = PERF_DETAIL_WIZARD;
    BrowseDlgData.szDialogBoxCaption = BROWSE_DIALOG_CAPTION;

    //
    // Add the selected counter to the query.
    //


    Status = PdhAddCounter(Query, CounterPathBuffer, 0, &Counter);
    if (Status != ERROR_SUCCESS) 
    {
        wprintf(L"\nPdhAddCounter failed with status 0x%x.", Status);
        goto Cleanup;
    }

    //
    // Most counters require two sample values to display a formatted value.
    // PDH stores the current sample value and the previously collected
    // sample value. This call retrieves the first value that will be used
    // by PdhGetFormattedCounterValue in the first iteration of the loop
    // Note that this value is lost if the counter does not require two
    // values to compute a displayable value.
    //

    Status = PdhCollectQueryData(Query);
    if (Status != ERROR_SUCCESS) 
    {
        wprintf(L"\nPdhCollectQueryData failed with 0x%x.\n", Status);
        goto Cleanup;
    }

    //
    // Print counter values until a key is pressed.
    //

    while (!_kbhit()) 
    {
        Sleep(SAMPLE_INTERVAL_MS);

        GetLocalTime(&SampleTime);

        Status = PdhCollectQueryData(Query);
        if (Status != ERROR_SUCCESS) 
        {
            wprintf(L"\nPdhCollectQueryData failed with status 0x%x.", Status);
        }

        wprintf(L"\n\"%2.2d/%2.2d/%4.4d %2.2d:%2.2d:%2.2d.%3.3d\"",
                SampleTime.wMonth,
                SampleTime.wDay,
                SampleTime.wYear,
                SampleTime.wHour,
                SampleTime.wMinute,
                SampleTime.wSecond,
                SampleTime.wMilliseconds);

        //
        // Compute a displayable value for the counter.
        //

        Status = PdhGetFormattedCounterValue(Counter,
                                             PDH_FMT_DOUBLE,
                                             &CounterType,
                                             &DisplayValue);
        if (Status != ERROR_SUCCESS) 
        {
            wprintf(L"\nPdhGetFormattedCounterValue failed with status 0x%x.", Status);
            goto Cleanup;
        }


        wprintf(L",\"%.20g\"", DisplayValue.doubleValue);
    }

Cleanup:

    //
    // Close the query.
    //

    if (Query) 
    {
       PdhCloseQuery(Query);
    }

    int x;
    cin >>x;
}

大部分代码来自此来源：msdn.microsoft.com/en-us/library/aa371886%28v=vs.85%29.aspx。我想缩短连续检查上下文切换之间的时间（使其少于一秒）。如果有人对如何做到这一点有任何想法，那就太好了。

Answer 2

在互联网上进行一点搜索，我发现这个名为“Performance Counters”的东西，您可以提供计数器数据或使用计数器数据。在您的情况下，我相信您想要从Performance Counters中读取数据。

您可以使用注册表界面或PDH界面来使用性能数据。 PDH界面比注册表界面更易于使用，建议用于大多数性能数据收集任务。 PDH接口本质上是注册表接口提供的功能的更高级抽象。

以下是Microsoft在Monitoring Context Switches上发表的另一篇文章。

Answer 3

如果您愿意，ETW（Windows事件跟踪）将为您提供有关上下文切换的更深入信息。代码可能比访问性能计数器复杂得多。

初始链接：Core OS Events in Windows 7和Windows Performance Toolkit Technical Reference

搜索字词：“ETW上下文切换”，“xperf”

计算Windows中特定进程的上下文切换

3 个答案: