在Linux上，你不能/不应该通过SysInfo的freeram或在totalram上做一些算术来获得“总的可用物理内存”。

推荐的方法是读取proc/meminfo，引用kernel/git/torvalds/linux。Git， /proc/meminfo提供估计可用内存:

许多负载平衡和工作负载放置程序检查/proc/meminfo到 估计有多少可用的空闲内存。他们通常这样做 把"免费"和"缓存"加起来，十年前还好，但现在 今天肯定是错的。

在/proc/meminfo中提供这样的估计更方便。如果将来事情发生改变，我们只需要在一个地方改变它。

一种方法是亚当·罗森菲尔德(Adam Rosenfield)对“如何确定c++中Linux系统RAM的数量?”建议:读取文件，并使用fscanf抓取行(但不是去MemTotal，去MemAvailable)

同样，如果你想要得到使用的物理内存总量，这取决于你对“使用”的定义，你可能不想从totalram中减去freeram，而是从memtotal中减去memavailable来得到top或htop告诉你的东西。

Linux

您还可以使用/proc/self/statm来获取一行包含关键进程内存信息的数字，这比从proc/self/status获取一长串报告信息要快得多

See, (5);

/proc/[pid]/statm

    Provides information about memory usage, measured in pages.
    The columns are:

        size       (1) total program size
                   (same as VmSize in /proc/[pid]/status)
        resident   (2) resident set size
                   (same as VmRSS in /proc/[pid]/status)
        shared     (3) number of resident shared pages (i.e., backed by a file)
                   (same as RssFile+RssShmem in /proc/[pid]/status)
        text       (4) text (code)
        lib        (5) library (unused since Linux 2.6; always 0)
        data       (6) data + stack
        dt         (7) dirty pages (unused since Linux 2.6; always 0)

在Linux上，你不能/不应该通过SysInfo的freeram或在totalram上做一些算术来获得“总的可用物理内存”。

推荐的方法是读取proc/meminfo，引用kernel/git/torvalds/linux。Git， /proc/meminfo提供估计可用内存:

许多负载平衡和工作负载放置程序检查/proc/meminfo到 估计有多少可用的空闲内存。他们通常这样做 把"免费"和"缓存"加起来，十年前还好，但现在 今天肯定是错的。

在/proc/meminfo中提供这样的估计更方便。如果将来事情发生改变，我们只需要在一个地方改变它。

一种方法是亚当·罗森菲尔德(Adam Rosenfield)对“如何确定c++中Linux系统RAM的数量?”建议:读取文件，并使用fscanf抓取行(但不是去MemTotal，去MemAvailable)

同样，如果你想要得到使用的物理内存总量，这取决于你对“使用”的定义，你可能不想从totalram中减去freeram，而是从memtotal中减去memavailable来得到top或htop告诉你的东西。

窗户

上面的一些值可以很容易地从适当的Win32 API中获得，为了完整起见，我只是在这里列出它们。但是，其他的需要从Performance Data Helper库(PDH)中获得，这有点“不直观”，并且需要大量痛苦的试验和错误才能开始工作。(至少我花了不少时间，也许我只是有点笨…)

注意:为了清晰起见，以下代码省略了所有错误检查。检查返回码…!

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(), (PROCESS_MEMORY_COUNTERS*)&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); // You can also use L"\\Processor(*)\\% Processor Time" and get individual CPU values with PdhGetFormattedCounterArray() PdhAddEnglishCounter(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

在Linux上，一开始似乎显而易见的选择是使用getrusage()等POSIX api。我花了一些时间试图让它工作，但从未得到有意义的值。当我最终检查内核源代码本身时，我发现显然这些api在Linux内核2.6中还没有完全实现!?

最后，通过读取伪文件系统/进程和内核调用，我得到了所有的值。

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){ // This assumes that a digit will be found and the line ends in " Kb". int i = strlen(line); const char* p = line; while (*p <'0' || *p > '9') p++; line[i-3] = '\0'; i = atoi(p); 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 %llu %llu %llu %llu", &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 %llu %llu %llu %llu", &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; }

待办事项:其他平台

我假设，除了读取/proc伪文件系统的部分之外，一些Linux代码也适用于unix。也许在Unix上，这些部分可以用getrusage()和类似的函数代替?

在Windows中，你可以通过下面的代码获取CPU使用情况:

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

//------------------------------------------------------------------------------------------------------------------
// Prototype(s)...
//------------------------------------------------------------------------------------------------------------------
CHAR cpuusage(void);

//-----------------------------------------------------
typedef BOOL ( __stdcall * pfnGetSystemTimes)( LPFILETIME lpIdleTime, LPFILETIME lpKernelTime, LPFILETIME lpUserTime );
static pfnGetSystemTimes s_pfnGetSystemTimes = NULL;

static HMODULE s_hKernel = NULL;
//-----------------------------------------------------
void GetSystemTimesAddress()
{
    if(s_hKernel == NULL)
    {
        s_hKernel = LoadLibrary(L"Kernel32.dll");
        if(s_hKernel != NULL)
        {
            s_pfnGetSystemTimes = (pfnGetSystemTimes)GetProcAddress(s_hKernel, "GetSystemTimes");
            if(s_pfnGetSystemTimes == NULL)
            {
                FreeLibrary(s_hKernel);
                s_hKernel = NULL;
            }
        }
    }
}
//----------------------------------------------------------------------------------------------------------------

//----------------------------------------------------------------------------------------------------------------
// cpuusage(void)
// ==============
// Return a CHAR value in the range 0 - 100 representing actual CPU usage in percent.
//----------------------------------------------------------------------------------------------------------------
CHAR cpuusage()
{
    FILETIME               ft_sys_idle;
    FILETIME               ft_sys_kernel;
    FILETIME               ft_sys_user;

    ULARGE_INTEGER         ul_sys_idle;
    ULARGE_INTEGER         ul_sys_kernel;
    ULARGE_INTEGER         ul_sys_user;

    static ULARGE_INTEGER     ul_sys_idle_old;
    static ULARGE_INTEGER  ul_sys_kernel_old;
    static ULARGE_INTEGER  ul_sys_user_old;

    CHAR usage = 0;

    // We cannot directly use GetSystemTimes in the C language
    /* Add this line :: pfnGetSystemTimes */
    s_pfnGetSystemTimes(&ft_sys_idle,    /* System idle time */
        &ft_sys_kernel,  /* system kernel time */
        &ft_sys_user);   /* System user time */

    CopyMemory(&ul_sys_idle  , &ft_sys_idle  , sizeof(FILETIME)); // Could been optimized away...
    CopyMemory(&ul_sys_kernel, &ft_sys_kernel, sizeof(FILETIME)); // Could been optimized away...
    CopyMemory(&ul_sys_user  , &ft_sys_user  , sizeof(FILETIME)); // Could been optimized away...

    usage  =
        (
        (
        (
        (
        (ul_sys_kernel.QuadPart - ul_sys_kernel_old.QuadPart)+
        (ul_sys_user.QuadPart   - ul_sys_user_old.QuadPart)
        )
        -
        (ul_sys_idle.QuadPart-ul_sys_idle_old.QuadPart)
        )
        *
        (100)
        )
        /
        (
        (ul_sys_kernel.QuadPart - ul_sys_kernel_old.QuadPart)+
        (ul_sys_user.QuadPart   - ul_sys_user_old.QuadPart)
        )
        );

    ul_sys_idle_old.QuadPart   = ul_sys_idle.QuadPart;
    ul_sys_user_old.QuadPart   = ul_sys_user.QuadPart;
    ul_sys_kernel_old.QuadPart = ul_sys_kernel.QuadPart;

    return usage;
}


//------------------------------------------------------------------------------------------------------------------
// Entry point
//------------------------------------------------------------------------------------------------------------------
int main(void)
{
    int n;
    GetSystemTimesAddress();
    for(n=0; n<20; n++)
    {
        printf("CPU Usage: %3d%%\r", cpuusage());
        Sleep(2000);
    }
    printf("\n");
    return 0;
}

Linux

读取内存和加载数的一种可移植方法是sysinfo调用

使用

   #include <sys/sysinfo.h>

   int sysinfo(struct sysinfo *info);

描述

   Until Linux 2.3.16, sysinfo() used to return information in the
   following structure:

       struct sysinfo {
           long uptime;             /* Seconds since boot */
           unsigned long loads[3];  /* 1, 5, and 15 minute load averages */
           unsigned long totalram;  /* Total usable main memory size */
           unsigned long freeram;   /* Available memory size */
           unsigned long sharedram; /* Amount of shared memory */
           unsigned long bufferram; /* Memory used by buffers */
           unsigned long totalswap; /* Total swap space size */
           unsigned long freeswap;  /* swap space still available */
           unsigned short procs;    /* Number of current processes */
           char _f[22];             /* Pads structure to 64 bytes */
       };

   and the sizes were given in bytes.

   Since Linux 2.3.23 (i386), 2.3.48 (all architectures) the structure
   is:

       struct sysinfo {
           long uptime;             /* Seconds since boot */
           unsigned long loads[3];  /* 1, 5, and 15 minute load averages */
           unsigned long totalram;  /* Total usable main memory size */
           unsigned long freeram;   /* Available memory size */
           unsigned long sharedram; /* Amount of shared memory */
           unsigned long bufferram; /* Memory used by buffers */
           unsigned long totalswap; /* Total swap space size */
           unsigned long freeswap;  /* swap space still available */
           unsigned short procs;    /* Number of current processes */
           unsigned long totalhigh; /* Total high memory size */
           unsigned long freehigh;  /* Available high memory size */
           unsigned int mem_unit;   /* Memory unit size in bytes */
           char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding to 64 bytes */
       };

   and the sizes are given as multiples of mem_unit bytes.