C++控制进程的系统资源

引言

在深度学习模型部署阶段，常常需要考虑硬件资源问题，如显存大小，IO读写速度CPU使用率，内存占用等问题，对于使用CPU环境的模型，这些问题显得更加重要。

这篇主要是针对 ONNXRUNTIME模型在 CPU环境下 C++部署时出现的CPU占用过高以及内存问题进行说明，并尝试解决。主要包含三个部分：

  • 编写占用CPU高的小程序，便于测试
  • 编写获取系统CPU使用率
  • 编写限制CPU使用率
  • 一些项目过程中的经验

Demo

主要通过循环的方式，占用CPU，另外由于处理器多核的缘故，需要创建线程来实现所有核心CPU的使用率跑满。

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// windows
#ifdef _WIN32
#define(_WIN32)
#include <windows.h>
#include <iostream>
#include <cstdlib>

using namespace std;

DWORD WINAPI FunProc(LPVOID lpParameter)
{
    float * p;

    while (p == p)
    {
        (*p++)+1.144564542315345;
    }
    return 0;
}

int main(int argc, char **argv)
{
    while(1){
    HANDLE hThread;
    for (int i = 0; i < 4; i++)
    {
        hThread = CreateThread(NULL, 0, FunProc, &i, 0, NULL);
        CloseHandle(hThread);
    }
}
    system("pause");
    return 0;
}
#elif defined(__GNUC__)
#include <unistd.h>

int main() {
    for(;;) { fork(); }
}
#endif

获取CPU信息

通过获取对应进程的 pid 实时监控CPU使用率，该例子支持跨平台。

  • linux下其实是通过读取并解析/proc目录下进程虚拟文件对应字段值计算得到
  • windows下调用系统api计算得到
  • 这种打点采样获取cpu和内存占用的方式数据跟用系统管理器查看到的不完全一致
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#include <iostream>
#include <thread>
#include <chrono>
#include <string.h>

#ifdef WIN32
#include <windows.h>  
#include <psapi.h>  
//#include <tlhelp32.h>
#include <direct.h>
#include <process.h>
#else
#include <sys/stat.h>
#include <sys/sysinfo.h>
#include <sys/time.h>
#include <unistd.h>
#endif

// get current process pid
inline int GetCurrentPid()
{
    return getpid();
}

// get specific process cpu occupation ratio by pid
#ifdef WIN32
// 
static uint64_t convert_time_format(const FILETIME* ftime)
{
    LARGE_INTEGER li;

    li.LowPart = ftime->dwLowDateTime;
    li.HighPart = ftime->dwHighDateTime;
    return li.QuadPart;
}
#else
// FIXME: can also get cpu and mem status from popen cmd
// the info line num in /proc/{pid}/status file
#define VMRSS_LINE 22
#define PROCESS_ITEM 14

static const char* get_items(const char* buffer, unsigned int item)
{
    // read from buffer by offset
    const char* p = buffer;

    int len = strlen(buffer);
    int count = 0;

    for (int i = 0; i < len; i++)
    {
        if (' ' == *p)
        {
            count++;
            if (count == item - 1)
            {
                p++;
                break;
            }
        }
        p++;
    }

    return p;
}

static inline unsigned long get_cpu_total_occupy()
{
    // get total cpu use time

    // different mode cpu occupy time
    unsigned long user_time;
    unsigned long nice_time;
    unsigned long system_time;
    unsigned long idle_time;

    FILE* fd;
    char buff[1024] = { 0 };

    fd = fopen("/proc/stat", "r");
    if (nullptr == fd)
        return 0;

    fgets(buff, sizeof(buff), fd);
    char name[64] = { 0 };
    sscanf(buff, "%s %ld %ld %ld %ld", name, &user_time, &nice_time, &system_time, &idle_time);
    fclose(fd);

    return (user_time + nice_time + system_time + idle_time);
}

static inline unsigned long get_cpu_proc_occupy(int pid)
{
    // get specific pid cpu use time
    unsigned int tmp_pid;
    unsigned long utime;  // user time
    unsigned long stime;  // kernel time
    unsigned long cutime; // all user time
    unsigned long cstime; // all dead time

    char file_name[64] = { 0 };
    FILE* fd;
    char line_buff[1024] = { 0 };
    sprintf(file_name, "/proc/%d/stat", pid);

    fd = fopen(file_name, "r");
    if (nullptr == fd)
        return 0;

    fgets(line_buff, sizeof(line_buff), fd);

    sscanf(line_buff, "%u", &tmp_pid);
    const char* q = get_items(line_buff, PROCESS_ITEM);
    sscanf(q, "%ld %ld %ld %ld", &utime, &stime, &cutime, &cstime);
    fclose(fd);

    return (utime + stime + cutime + cstime);
}
#endif

inline float GetCpuUsageRatio(int pid)
{
#ifdef WIN32
    static int64_t last_time = 0;
    static int64_t last_system_time = 0;

    FILETIME now;
    FILETIME creation_time;
    FILETIME exit_time;
    FILETIME kernel_time;
    FILETIME user_time;
    int64_t system_time;
    int64_t time;
    int64_t system_time_delta;
    int64_t time_delta;

    // get cpu num
    SYSTEM_INFO info;
    GetSystemInfo(&info);
    int cpu_num = info.dwNumberOfProcessors;

    float cpu_ratio = 0.0;

    // get process hanlde by pid
    HANDLE process = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
    // use GetCurrentProcess() can get current process and no need to close handle

    // get now time
    GetSystemTimeAsFileTime(&now);

    if (!GetProcessTimes(process, &creation_time, &exit_time, &kernel_time, &user_time))
    {
        // We don't assert here because in some cases (such as in the Task Manager)  
        // we may call this function on a process that has just exited but we have  
        // not yet received the notification.  
        printf("GetCpuUsageRatio GetProcessTimes failed\n");
        return 0.0;
    }

    // should handle the multiple cpu num
    system_time = (convert_time_format(&kernel_time) + convert_time_format(&user_time)) / cpu_num;
    time = convert_time_format(&now);

    if ((last_system_time == 0) || (last_time == 0))
    {
        // First call, just set the last values.  
        last_system_time = system_time;
        last_time = time;
        return 0.0;
    }

    system_time_delta = system_time - last_system_time;
    time_delta = time - last_time;

    CloseHandle(process);

    if (time_delta == 0)
    {
        printf("GetCpuUsageRatio time_delta is 0, error\n");
        return 0.0;
    }

    // We add time_delta / 2 so the result is rounded.  
    cpu_ratio = (int)((system_time_delta * 100 + time_delta / 2) / time_delta); // the % unit
    last_system_time = system_time;
    last_time = time;

    cpu_ratio /= 100.0; // convert to float number

    return cpu_ratio;
#else
    unsigned long totalcputime1, totalcputime2;
    unsigned long procputime1, procputime2;

    totalcputime1 = get_cpu_total_occupy();
    procputime1 = get_cpu_proc_occupy(pid);

    // FIXME: the 200ms is a magic number, works well
    usleep(200000); // sleep 200ms to fetch two time point cpu usage snapshots sample for later calculation

    totalcputime2 = get_cpu_total_occupy();
    procputime2 = get_cpu_proc_occupy(pid);

    float pcpu = 0.0;
    if (0 != totalcputime2 - totalcputime1)
        pcpu = (procputime2 - procputime1) / float(totalcputime2 - totalcputime1); // float number

    int cpu_num = get_nprocs();
    pcpu *= cpu_num; // should multiply cpu num in multiple cpu machine

    return pcpu;
#endif
}

// get specific process physical memeory occupation size by pid (MB)
inline float GetMemoryUsage(int pid)
{
#ifdef WIN32
    uint64_t mem = 0, vmem = 0;
    PROCESS_MEMORY_COUNTERS pmc;

    // get process hanlde by pid
    HANDLE process = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
    if (GetProcessMemoryInfo(process, &pmc, sizeof(pmc)))
    {
        mem = pmc.WorkingSetSize;
        vmem = pmc.PagefileUsage;
    }
    CloseHandle(process);

    // use GetCurrentProcess() can get current process and no need to close handle

    // convert mem from B to MB
    return mem / 1024.0 / 1024.0;

#else
    char file_name[64] = { 0 };
    FILE* fd;
    char line_buff[512] = { 0 };
    sprintf(file_name, "/proc/%d/status", pid);

    fd = fopen(file_name, "r");
    if (nullptr == fd)
        return 0;

    char name[64];
    int vmrss = 0;
    for (int i = 0; i < VMRSS_LINE - 1; i++)
        fgets(line_buff, sizeof(line_buff), fd);

    fgets(line_buff, sizeof(line_buff), fd);
    sscanf(line_buff, "%s %d", name, &vmrss);
    fclose(fd);

    // cnvert VmRSS from KB to MB
    return vmrss / 1024.0;
#endif
}

int main()
{
    // launch some task to occupy cpu and memory
    for (int i = 0; i < 5; i++)
        std::thread([]
            {
                std::this_thread::sleep_for(std::chrono::milliseconds(10));
            }).detach();

    int current_pid = GetCurrentPid(); // or you can set a outside program pid
    float cpu_usage_ratio = GetCpuUsageRatio(current_pid);
    float memory_usage = GetMemoryUsage(current_pid);

    while (true)
    {
        std::cout << "current pid: " << current_pid << std::endl;
        std::cout << "cpu usage ratio: " << cpu_usage_ratio * 100 << "%" << std::endl;
        std::cout << "memory usage: " << memory_usage << "MB" << std::endl;

        std::this_thread::sleep_for(std::chrono::milliseconds(1000));
    }

    return 0;
}

运行效果

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current pid: 1476528
cpu usage ratio: 0%
memory usage: 4.83984MB

资源控制

Windows提供了一个叫做 JobObject的东东，可以限制进程的 CPU利用率、CPU核心、内存、网络带宽、管理员权限等等。

使用流程如下：

  1. 通过 CreateJobObjectA创建一个 JobObject
  2. 创建一个job information的结构体，设置自己要控制的值。有很多不同的结构体声明，分别用来控制不同的属性
  3. 通过 SetInformationJobObject来将刚才创建的information设给JobObject
  4. 通过 AssignProcessToJobObject来将某个进程分配给Job Object，这样，这个进程就会受到Job Object的控制了

注意限制子进程不需要管理员权限。如果要限制已经存在的进程，就需要用管理员权限运行。

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#include <windows.h>
#include <stdexcept>
#include <iostream>
#include <string>
using namespace std::string_literals;

class Process
{
public:
    Process() = default;
    Process(const Process&) = delete;
    Process operator=(const Process&) = delete;
    virtual ~Process() {};
    virtual HANDLE handle() const = 0;
    virtual void wait() const = 0;
};

class AttachProcess : public Process
{
private:
    HANDLE h;
public:
    explicit AttachProcess(DWORD pid)
    {
        h = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
        if (h == NULL)
            throw std::runtime_error("Failed to open process");
    }
    ~AttachProcess() { CloseHandle(h); }
    HANDLE handle() const override { return h; }
    void wait() const override
    {
        WaitForSingleObject(h, INFINITE);
    }
};

class ChildProcess : public Process
{
private:
    STARTUPINFOA si;
    PROCESS_INFORMATION pi;
public:
    ChildProcess(const ChildProcess&) = delete;
    ChildProcess operator=(const ChildProcess&) = delete;
    explicit ChildProcess(LPCSTR applicationPath)
    {
        ZeroMemory(&si, sizeof(si));
        si.cb = sizeof(si);
        ZeroMemory(&pi, sizeof(pi));
        if (!CreateProcessA(applicationPath,
            NULL, NULL, NULL, FALSE, CREATE_SUSPENDED, NULL, NULL,
            &si, &pi))
        {
            throw std::runtime_error("Failed to create child process!");
        }
    }
    void start()
    {
        ResumeThread(pi.hThread);
    }
    void wait() const override
    {
        WaitForSingleObject(pi.hProcess, INFINITE);
    }
    HANDLE handle() const override
    {
        return pi.hProcess;
    }
    ~ChildProcess()
    {
        WaitForSingleObject(pi.hProcess, INFINITE);
        CloseHandle(pi.hProcess);
        CloseHandle(pi.hThread);
    }
};

class JobObjectInformation
{
public:
    JobObjectInformation() = default;
    JobObjectInformation(const JobObjectInformation&) = delete;
    JobObjectInformation operator=(const JobObjectInformation&) = delete;
    virtual JOBOBJECTINFOCLASS getClass() const = 0;
    virtual DWORD length() const = 0;
    virtual LPVOID informationPtr() const = 0;
    virtual ~JobObjectInformation() {};
};


class JobObject
{
public:
    JobObject(const JobObject&) = delete;
    JobObject operator=(const JobObject&) = delete;
    JobObject()
    {
        jobHandle = CreateJobObjectA(NULL, NULL);
        if (jobHandle == NULL) {
            throw std::runtime_error("Create job failed!");
        }
    }
    HANDLE getHandle()
    {
        return jobHandle;
    }
    void assignProcess(const Process &p)
    {
        if (AssignProcessToJobObject(jobHandle, p.handle()) == 0)
            throw std::runtime_error("Failed to assgin process to job: "s + std::to_string(GetLastError()));
    }
    BOOL setInformation(const JobObjectInformation& i)
    {
        return SetInformationJobObject(jobHandle, i.getClass(), i.informationPtr(), i.length());
    }
    ~JobObject()
    {
        CloseHandle(jobHandle);
    }

private:
    HANDLE jobHandle{};
};



class CpuRateJobObjectInformation : public JobObjectInformation
{
public:
    CpuRateJobObjectInformation(int rate)
    {
        information.ControlFlags = JOB_OBJECT_CPU_RATE_CONTROL_ENABLE | JOB_OBJECT_CPU_RATE_CONTROL_HARD_CAP;
        if (rate <= 0 || rate > 100)
            throw std::runtime_error("Invalid argument");
        information.CpuRate = rate * 100;
    }
    virtual JOBOBJECTINFOCLASS getClass() const override
    {
        return JOBOBJECTINFOCLASS::JobObjectCpuRateControlInformation;
    }
    virtual DWORD length() const override
    {
        return sizeof(information);
    }
    virtual LPVOID informationPtr() const override
    {
        return (LPVOID) &information;
    }
private:
    JOBOBJECT_CPU_RATE_CONTROL_INFORMATION information{};
};

int main(int argc, const char **argv)
{
    JobObject jobObject;
    CpuRateJobObjectInformation information{20};
    jobObject.setInformation(information);
    // 通过直接打开程序来限制
    ChildProcess childProcess{ "c:\\测试demo.exe"};

    jobObject.assignProcess(childProcess);
    childProcess.start();
    childProcess.wait();

    // 通过运行程序的PID来限制
    DWORD pid;
    std::cout << "Input PID:" << std::endl;
    std::cin >> pid;
    AttachProcess attachProcess{ pid };
    try
    {
        jobObject.assignProcess(attachProcess);
    }
    catch (const std::exception& e)
    {
        std::cout << e.what();
    }
    attachProcess.wait();
    return 0;
}

经验

以上的方式都是在程序外部去做限制，对于资源被控程序的内部，就是这部分功能有源码，可以先排查问题，比如是哪一部分CPU占用的资源比较大，可以通过工具去分析，如 VS探查器 ,其他的工具有需要后续再详细说明。

思路说明：

CPU占用过高，一般是发生在循环内部，或则多线程占用了资源。

既然知道了原因，那么就有对应的解决办法：

  1. 优化循环部分的程序，看是否能简化循环步骤或利用硬件特性（比如在一个循环内同时处理多个数据）来解决
  2. sleep(0)的妙用，让出剩余资源控制权限

另一种也是在程序外处理：

  1. 绑定线程到指定的CPU核心

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    //Thread 0 can only run on CPU 0.  

    SetThreadAffinityMask(hThread0, 0x00000001); //第0位是1  

    //Threads 1, 2, 3 run on CPUs 1, 2, 3.//第1 2 3位是1  

    SetThreadAffinityMask(hThread1, 0x00000002);  

    SetThreadAffinityMask(hThread2, 0x00000003);  

    SetThreadAffinityMask(hThread3, 0x00000004);

  2. 设置优先级

    具体的内容见参考5

以上就是工程中的一些经验分享，深入的可在交流，对于深度学习模型在CPU上跑满CPU资源的开发们，可以尝试这种方式，避免电脑卡死。

参考

  1. https://zhuanlan.zhihu.com/p/266839249
  2. https://zhuanlan.zhihu.com/p/498134424
  3. https://blog.csdn.net/qiaoquan3/article/details/56281092
  4. https://www.cnblogs.com/kex1n/archive/2011/05/09/2040924.html
  5. https://blog.csdn.net/youshijian99/article/details/79682054