C++ 獲取 CPU 使用率：Windows PDH 與 Linux /proc/stat 方案

Windows 方案：PDH (Performance Data Helper)

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

double GetCpuUsage() {
    PDH_HQUERY query;
    PDH_HCOUNTER counter;
    PdhOpenQuery(NULL, 0, &query);
    PdhAddEnglishCounter(query, "\\Processor(_Total)\\% Processor Time", 0, &counter);
    PdhCollectQueryData(query);
    Sleep(1000); // 採樣間隔
    PdhCollectQueryData(query);
    PDH_FMT_COUNTERVALUE value;
    PdhGetFormattedCounterValue(counter, PDH_FMT_DOUBLE, NULL, &value);
    PdhCloseQuery(query);
    return value.doubleValue;
}

Linux 方案：解析 /proc/stat

#include 
#include 
#include 
#include 
#include 

double GetCpuUsageLinux() {
    auto readCpuTimes = []() {
        std::ifstream f("/proc/stat");
        std::string line;
        std::getline(f, line); // cpu  123 45 67 ...
        std::istringstream iss(line.substr(5));
        long val; std::vector times;
        while (iss >> val) times.push_back(val);
        return times; // user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice
    };

    auto t1 = readCpuTimes();
    std::this_thread::sleep_for(std::chrono::milliseconds(500));
    auto t2 = readCpuTimes();

    long idle1 = t1[3], total1 = 0; for (auto v : t1) total1 += v;
    long idle2 = t2[3], total2 = 0; for (auto v : t2) total2 += v;

    return 100.0 * (1.0 - double(idle2 - idle1) / (total2 - total1));
}

跨平台封裝建議

class CpuMonitor {
public:
    static double GetUsage() {
#if defined(_WIN32)
        return GetCpuUsageWin();
#elif defined(__linux__)
        return GetCpuUsageLinux();
#else
        return -1.0;
#endif
    }
};

注意事項

• Windows 需鏈接 pdh.lib，且首次調用需預熱一次。
• Linux 容器環境下 /proc/stat 反映宿主機 CPU，若需容器限額請讀 /sys/fs/cgroup/cpu/cpu.stat。
• 多核心邏輯 CPU 使用率已包含在總值中，如需單核請解析 cpu0, cpu1... 行。