将性能数据写入日志文件

以下示例将实时性能数据写入日志文件。 该示例调用 PdhOpenQuery 和 PdhAddCounter 函数来创建查询以收集处理器时间计数器数据。 然后，该示例调用 PdhOpenLog 函数来创建要将数据写入的日志文件。 该示例调用 PdhUpdateLog 函数来收集示例，并每秒更新一次日志文件，持续 20 秒。

有关读取生成的日志文件的示例，请参阅 从日志文件读取性能数据。

#include <windows.h>
#include <stdio.h>
#include <pdh.h>
#include <pdhmsg.h>

#pragma comment(lib, "pdh.lib")

CONST PWSTR COUNTER_PATH    = L"\\Processor(0)\\% Processor Time";
CONST ULONG SAMPLE_INTERVAL_MS = 1000;

void DisplayCommandLineHelp(void)
{
    wprintf(L"The command line must include a valid log file name.\n"); 
}

void wmain(int argc, WCHAR **argv)
{
    HQUERY hQuery = NULL;
    HLOG hLog = NULL;
    PDH_STATUS pdhStatus;
    DWORD dwLogType = PDH_LOG_TYPE_CSV;
    HCOUNTER hCounter;
    DWORD dwCount;

    if (argc != 2) 
    {
        DisplayCommandLineHelp();
        goto cleanup;
    }

    // Open a query object.
    pdhStatus = PdhOpenQuery(NULL, 0, &hQuery);

    if (pdhStatus != ERROR_SUCCESS)
    {
        wprintf(L"PdhOpenQuery failed with 0x%x\n", pdhStatus);
        goto cleanup;
    }

    // Add one counter that will provide the data.
    pdhStatus = PdhAddCounter(hQuery,
        COUNTER_PATH,
        0,
        &hCounter);

    if (pdhStatus != ERROR_SUCCESS)
    {
        wprintf(L"PdhAddCounter failed with 0x%x\n", pdhStatus);
        goto cleanup;
    }

    // Open the log file for write access.
    pdhStatus = PdhOpenLog(argv[1], 
        PDH_LOG_WRITE_ACCESS | PDH_LOG_CREATE_ALWAYS,
        &dwLogType,
        hQuery,
        0, 
        NULL,
        &hLog);

    if (pdhStatus != ERROR_SUCCESS)
    {
        wprintf(L"PdhOpenLog failed with 0x%x\n", pdhStatus);
        goto cleanup;
    }
 
    // Write 10 records to the log file.
    for (dwCount = 0; dwCount < 10; dwCount++) 
    {
        wprintf(L"Writing record %d\n", dwCount);

        pdhStatus = PdhUpdateLog (hLog, NULL);
        if (ERROR_SUCCESS != pdhStatus)
        {
            wprintf(L"PdhUpdateLog failed with 0x%x\n", pdhStatus);
            goto cleanup;
        }

        // Wait one second between samples for a counter update.
        Sleep(SAMPLE_INTERVAL_MS); 
    }

cleanup:

    // Close the log file.
    if (hLog)
        PdhCloseLog (hLog, 0);

    // Close the query object.
    if (hQuery)
        PdhCloseQuery (hQuery);
}