How to determine CPU and memory consumption from inside a process

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本文详细介绍了如何在Windows和Linux环境下获取系统资源使用情况的方法，包括总虚拟内存、当前使用的虚拟内存、当前进程使用的虚拟内存、总物理内存、当前使用的物理内存、当前进程使用的物理内存以及CPU使用率等。

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Total virtual memory available
Virtual memory currently used
Virtual memory currently used by my process
Total RAM available
RAM currently used
RAM currently used by my process
% CPU currently used
% CPU currently used by my process

Windows

Some of the above values are easily available from the appropriate WIN32 API, I just list them here for completeness. Others, however, need to be obtained from the Performance Data Helper libary (PDH), which is a bit "unintuitive" and takes a lot of painful trial and error to get to work. (At least it took me quite a while, perhaps I've been only a bit stupid...)

Note: for clarity all error checking has been omitted from the following code. Do check the return codes...!

Total Virtual Memory:


    #include "windows.h"
    

    MEMORYSTATUSEX memInfo;
    memInfo.dwLength = sizeof(MEMORYSTATUSEX);
    GlobalMemoryStatusEx(&memInfo);
    DWORDLONG totalVirtualMem = memInfo.ullTotalPageFile;

Note: The name "TotalPageFile" is a bit misleading here. In reality this parameter gives the "Virtual Memory Size", which is size of swap file plus installed RAM.

Virtual Memory currently used:

Same code as in "Total Virtual Memory" and then


    DWORDLONG virtualMemUsed = memInfo.ullTotalPageFile - memInfo.ullAvailPageFile;

Virtual Memory currently used by current process:


    #include "windows.h"
    #include "psapi.h"
    

    PROCESS_MEMORY_COUNTERS_EX pmc;
    GetProcessMemoryInfo(GetCurrentProcess(), &pmc, sizeof(pmc));
    SIZE_T virtualMemUsedByMe = pmc.PrivateUsage;

Total Physical Memory (RAM):

Same code as in "Total Virtual Memory" and then


    DWORDLONG totalPhysMem = memInfo.ullTotalPhys;

Physical Memory currently used:

Same code as in "Total Virtual Memory" and then


    DWORDLONG physMemUsed = memInfo.ullTotalPhys - memInfo.ullAvailPhys;

Physical Memory currently used by current process:

Same code as in "Virtual Memory currently used by current process" and then


    SIZE_T physMemUsedByMe = pmc.WorkingSetSize;

CPU currently used:


    #include "TCHAR.h"
    #include "pdh.h"
    

    static PDH_HQUERY cpuQuery;
    static PDH_HCOUNTER cpuTotal;
    

    void init(){
        PdhOpenQuery(NULL, NULL, &cpuQuery);
        PdhAddCounter(cpuQuery, L"\\Processor(_Total)\\% Processor Time", NULL, &cpuTotal);
        PdhCollectQueryData(cpuQuery);
    }
    

    double getCurrentValue(){
        PDH_FMT_COUNTERVALUE counterVal;
    

        PdhCollectQueryData(cpuQuery);
        PdhGetFormattedCounterValue(cpuTotal, PDH_FMT_DOUBLE, NULL, &counterVal);
        return counterVal.doubleValue;
    }

CPU currently used by current process:


    #include "windows.h"
    

    static ULARGE_INTEGER lastCPU, lastSysCPU, lastUserCPU;
    static int numProcessors;
    static HANDLE self;
    

    void init(){
        SYSTEM_INFO sysInfo;
        FILETIME ftime, fsys, fuser;
    

        GetSystemInfo(&sysInfo);
        numProcessors = sysInfo.dwNumberOfProcessors;
    

        GetSystemTimeAsFileTime(&ftime);
        memcpy(&lastCPU, &ftime, sizeof(FILETIME));
    

        self = GetCurrentProcess();
        GetProcessTimes(self, &ftime, &ftime, &fsys, &fuser);
        memcpy(&lastSysCPU, &fsys, sizeof(FILETIME));
        memcpy(&lastUserCPU, &fuser, sizeof(FILETIME));
    }
    

    double getCurrentValue(){
        FILETIME ftime, fsys, fuser;
        ULARGE_INTEGER now, sys, user;
        double percent;
    

        GetSystemTimeAsFileTime(&ftime);
        memcpy(&now, &ftime, sizeof(FILETIME));
    

        GetProcessTimes(self, &ftime, &ftime, &fsys, &fuser);
        memcpy(&sys, &fsys, sizeof(FILETIME));
        memcpy(&user, &fuser, sizeof(FILETIME));
        percent = (sys.QuadPart - lastSysCPU.QuadPart) +
            (user.QuadPart - lastUserCPU.QuadPart);
        percent /= (now.QuadPart - lastCPU.QuadPart);
        percent /= numProcessors;
        lastCPU = now;
        lastUserCPU = user;
        lastSysCPU = sys;
    

        return percent * 100;
    }

Linux

On Linux the choice that seemed obvious at first was to use the POSIX APIs like getrusage() etc. I spent some time trying to get this to work, but never got meaningful values. When I finally checked the kernel sources themselves, I found out that apparently these APIs are not yet completely implemented as of Linux kernel 2.6!?

In the end I got all values via a combination of reading the pseudo-filesystem /proc and kernel calls.

Total Virtual Memory:


    #include "sys/types.h"
    #include "sys/sysinfo.h"
    

    struct sysinfo memInfo;
    

    sysinfo (&memInfo);
    long long totalVirtualMem = memInfo.totalram;
    //Add other values in next statement to avoid int overflow on right hand side...
    totalVirtualMem += memInfo.totalswap;
    totalVirtualMem *= memInfo.mem_unit;

Virtual Memory currently used:

Same code as in "Total Virtual Memory" and then


    long long virtualMemUsed = memInfo.totalram - memInfo.freeram;
    //Add other values in next statement to avoid int overflow on right hand side...
    virtualMemUsed += memInfo.totalswap - memInfo.freeswap;
    virtualMemUsed *= memInfo.mem_unit;

Virtual Memory currently used by current process:


    #include "stdlib.h"
    #include "stdio.h"
    #include "string.h"
    

    int parseLine(char* line){
        int i = strlen(line);
        while (*line < '0' || *line > '9') line++;
        line[i-3] = '\0';
        i = atoi(line);
        return i;
    }
    

    int getValue(){ //Note: this value is in KB!
        FILE* file = fopen("/proc/self/status", "r");
        int result = -1;
        char line[128];
    

        while (fgets(line, 128, file) != NULL){
            if (strncmp(line, "VmSize:", 7) == 0){
                result = parseLine(line);
                break;
            }
        }
        fclose(file);
        return result;
    }

Total Physical Memory (RAM):

Same code as in "Total Virtual Memory" and then


    long long totalPhysMem = memInfo.totalram;
    //Multiply in next statement to avoid int overflow on right hand side...
    totalPhysMem *= memInfo.mem_unit;

Physical Memory currently used:

Same code as in "Total Virtual Memory" and then


    long long physMemUsed = memInfo.totalram - memInfo.freeram;
    //Multiply in next statement to avoid int overflow on right hand side...
    physMemUsed *= memInfo.mem_unit;

Physical Memory currently used by current process:

Change getValue() in "Virtual Memory currently used by current process" as follows:


    int getValue(){ //Note: this value is in KB!
        FILE* file = fopen("/proc/self/status", "r");
        int result = -1;
        char line[128];
    

        while (fgets(line, 128, file) != NULL){
            if (strncmp(line, "VmRSS:", 6) == 0){
                result = parseLine(line);
                break;
            }
        }
        fclose(file);
        return result;
    }

CPU currently used:


    #include "stdlib.h"
    #include "stdio.h"
    #include "string.h"
    

    static unsigned long long lastTotalUser, lastTotalUserLow, lastTotalSys, lastTotalIdle;
    

    void init(){
        FILE* file = fopen("/proc/stat", "r");
        fscanf(file, "cpu %Ld %Ld %Ld %Ld", &lastTotalUser, &lastTotalUserLow,
            &lastTotalSys, &lastTotalIdle);
        fclose(file);
    }
    

    double getCurrentValue(){
        double percent;
        FILE* file;
        unsigned long long totalUser, totalUserLow, totalSys, totalIdle, total;
    

        file = fopen("/proc/stat", "r");
        fscanf(file, "cpu %Ld %Ld %Ld %Ld", &totalUser, &totalUserLow,
            &totalSys, &totalIdle);
        fclose(file);
    

        if (totalUser < lastTotalUser || totalUserLow < lastTotalUserLow ||
            totalSys < lastTotalSys || totalIdle < lastTotalIdle){
            //Overflow detection. Just skip this value.
            percent = -1.0;
        }
        else{
            total = (totalUser - lastTotalUser) + (totalUserLow - lastTotalUserLow) +
                (totalSys - lastTotalSys);
            percent = total;
            total += (totalIdle - lastTotalIdle);
            percent /= total;
            percent *= 100;
        }
    

        lastTotalUser = totalUser;
        lastTotalUserLow = totalUserLow;
        lastTotalSys = totalSys;
        lastTotalIdle = totalIdle;
    

        return percent;
    }

CPU currently used by current process:


    #include "stdlib.h"
    #include "stdio.h"
    #include "string.h"
    #include "sys/times.h"
    #include "sys/vtimes.h"
    

    static clock_t lastCPU, lastSysCPU, lastUserCPU;
    static int numProcessors;
    

    void init(){
        FILE* file;
        struct tms timeSample;
        char line[128];
    

        lastCPU = times(&timeSample);
        lastSysCPU = timeSample.tms_stime;
        lastUserCPU = timeSample.tms_utime;
    

        file = fopen("/proc/cpuinfo", "r");
        numProcessors = 0;
        while(fgets(line, 128, file) != NULL){
            if (strncmp(line, "processor", 9) == 0) numProcessors++;
        }
        fclose(file);
    }
    

    double getCurrentValue(){
        struct tms timeSample;
        clock_t now;
        double percent;
    

        now = times(&timeSample);
        if (now <= lastCPU || timeSample.tms_stime < lastSysCPU ||
            timeSample.tms_utime < lastUserCPU){
            //Overflow detection. Just skip this value.
            percent = -1.0;
        }
        else{
            percent = (timeSample.tms_stime - lastSysCPU) +
                (timeSample.tms_utime - lastUserCPU);
            percent /= (now - lastCPU);
            percent /= numProcessors;
            percent *= 100;
        }
        lastCPU = now;
        lastSysCPU = timeSample.tms_stime;
        lastUserCPU = timeSample.tms_utime;
    

        return percent;
    }