How to determine CPU and memory consumption from inside a process

Question

I once had the task of determining the following performance parameters from inside a running application    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   The code had to run on Windows and Linux  Even though this seems to be a standard task  finding the necessary information in the manuals  WIN32 API  GNU docs  as well as on the Internet took me several days  because there s so much incomplete incorrect outdated information on this topic to be found out there   In order to save others from going through the same trouble  I thought it would be a good idea to collect all the scattered information plus what I found by trial and error here in one place

User · Answer

For Linux You can also use  proc self statm to get a single line of numbers containing key process memory information which is a faster thing to process than going through a long list of reported information as you get from proc self status  See http   man7 org linux man-pages man5 proc 5 html      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

User · Answer

in windows you can get cpu usage by code bellow    include  lt windows h gt   include  lt stdio h gt         ------------------------------------------------------------------------------------------------------------------        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 on C language            add this line    pfnGetSystemTimes            s pfnGetSystemTimes  amp ft sys idle        System idle time                 amp ft sys kernel      system kernel time                 amp ft sys user        System user time             CopyMemory  amp ul sys idle     amp ft sys idle    sizeof FILETIME       Could been optimized away            CopyMemory  amp ul sys kernel   amp ft sys kernel  sizeof FILETIME       Could been optimized away            CopyMemory  amp ul sys user     amp 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 lt 20 n                          printf  CPU Usage   3d   r  cpuusage                 Sleep 2000                     printf   n            return 0

User · Answer

Linux  In Linux  this information is available in the  proc file system   I m not a big fan of the text file format used  as each Linux distribution seems to customize at least one important file   A quick look as the source to  ps  reveals the mess   But here is where to find the information you seek    proc meminfo contains the majority of the system-wide information you seek   Here it looks like on my system  I think you are interested in MemTotal  MemFree  SwapTotal  and SwapFree   Anderson cxc   more  proc meminfo MemTotal       4083948 kB MemFree        2198520 kB Buffers          82080 kB Cached         1141460 kB SwapCached           0 kB Active         1137960 kB Inactive        608588 kB HighTotal      3276672 kB HighFree       1607744 kB LowTotal        807276 kB LowFree         590776 kB SwapTotal      2096440 kB SwapFree       2096440 kB Dirty               32 kB Writeback            0 kB AnonPages       523252 kB Mapped           93560 kB Slab             52880 kB SReclaimable     24652 kB SUnreclaim       28228 kB PageTables        2284 kB NFS Unstable         0 kB Bounce               0 kB CommitLimit    4138412 kB Committed AS   1845072 kB VmallocTotal    118776 kB VmallocUsed       3964 kB VmallocChunk    112860 kB HugePages Total      0 HugePages Free       0 HugePages Rsvd       0 Hugepagesize      2048 kB   For CPU utilization  you have to do a little work   Linux makes available overall CPU utilization since system start  this probably isn t what you are interested in   If you want to know what the CPU utilization was for the last second  or 10 seconds  then you need to query the information and calculate it yourself   The information is available in  proc stat  which is documented pretty well at http   www linuxhowtos org System procstat htm  here is what it looks like on my 4-core box   Anderson cxc    more  proc stat cpu  2329889 0 2364567 1063530460 9034 9463 96111 0 cpu0 572526 0 636532 265864398 2928 1621 6899 0 cpu1 590441 0 531079 265949732 4763 351 8522 0 cpu2 562983 0 645163 265796890 682 7490 71650 0 cpu3 603938 0 551790 265919440 660 0 9040 0 intr 37124247 ctxt 50795173133 btime 1218807985 processes 116889 procs running 1 procs blocked 0   First  you need to determine how many CPUs  or processors  or processing cores  are available in the system   To do this  count the number of  cpuN  entries  where N starts at 0 and increments   Don t count the  cpu  line  which is a combination of the cpuN lines   In my example  you can see cpu0 through cpu3  for a total of 4 processors   From now on  you can ignore cpu0  cpu3  and focus only on the  cpu  line   Next  you need to know that the fourth number in these lines is a measure of idle time  and thus the fourth number on the  cpu  line is the total idle time for all processors since boot time   This time is measured in Linux  jiffies   which are 1 100 of a second each    But you don t care about the total idle time  you care about the idle time in a given period  e g   the last second   Do calculate that  you need to read this file twice  1 second apart Then you can do a diff of the fourth value of the line   For example  if you take a sample and get   cpu  2330047 0 2365006 1063853632 9035 9463 96114 0   Then one second later you get this sample   cpu  2330047 0 2365007 1063854028 9035 9463 96114 0   Subtract the two numbers  and you get a diff of 396  which means that your CPU had been idle for 3 96 seconds out of the last 1 00 second   The trick  of course  is that you need to divide by the number of processors   3 96   4   0 99  and there is your idle percentage  99  idle  and 1  busy   In my code  I have a ring buffer of 360 entries  and I read this file every second   That lets me quickly calculate the CPU utilization for 1 second  10 seconds  etc   all the way up to 1 hour   For the process-specific information  you have to look in  proc pid  if you don t care abut your pid  you can look in  proc self   CPU used by your process is available in  proc self stat   This is an odd-looking file consisting of a single line  for example   19340  whatever  S 19115 19115 3084 34816 19115 4202752 118200 607 0 0 770 384 2  7 20 0 77 0 266764385 692477952 105074 4294967295 134512640 146462952 321468364 8 3214683328 4294960144 0 2147221247 268439552 1276 4294967295 0 0 17 0 0 0 0   The important data here are the 13th and 14th tokens  0 and 770 here    The 13th token is the number of jiffies that the process has executed in user mode  and the 14th is the number of jiffies that the process has executed in kernel mode   Add the two together  and you have its total CPU utilization   Again  you will have to sample this file periodically  and calculate the diff  in order to determine the process s CPU usage over time     Edit   remember that when you calculate your process s CPU utilization  you have to take into account 1  the number of threads in your process  and 2  the number of processors in the system   For example  if your single-threaded process is using only 25  of the CPU  that could be good or bad   Good on a single-processor system  but bad on a 4-processor system  this means that your process is running constantly  and using 100  of the CPU cycles available to it   For the process-specific memory information  you ahve to look at  proc self status  which looks like this   Name    whatever State   S  sleeping  Tgid    19340 Pid     19340 PPid    19115 TracerPid       0 Uid     0       0       0       0 Gid     0       0       0       0 FDSize  256 Groups  0 1 2 3 4 6 10 11 20 26 27 VmPeak    676252 kB VmSize    651352 kB VmLck          0 kB VmHWM     420300 kB VmRSS     420296 kB VmData    581028 kB VmStk        112 kB VmExe      11672 kB VmLib      76608 kB VmPTE       1244 kB Threads         77 SigQ    0 36864 SigPnd  0000000000000000 ShdPnd  0000000000000000 SigBlk  fffffffe7ffbfeff SigIgn  0000000010001000 SigCgt  20000001800004fc CapInh  0000000000000000 CapPrm  00000000ffffffff CapEff  00000000fffffeff Cpus allowed    0f Mems allowed    1 voluntary ctxt switches         6518 nonvoluntary ctxt switches      6598   The entries that start with  Vm  are the interesting ones    VmPeak is the maximum virtual memory space used by the process  in kB  1024 bytes   VmSize is the current virtual memory space used by the process  in kB   In my example  it s pretty large   651 352 kB  or about 636 megabytes  VmRss is the amount of memory that have been mapped into the process  address space  or its resident set size   This is substantially smaller  420 296 kB  or about 410 megabytes    The difference   my program has mapped 636 MB via mmap    but has only accessed 410 MB of it  and thus only 410 MB of pages have been assigned to it    The only item I m not sure about is Swapspace currently used by my process   I don t know if this is available

User · Answer

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 library  PDH   which is a bit  quot unintuitive quot  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  quot windows h quot   MEMORYSTATUSEX memInfo  memInfo dwLength   sizeof MEMORYSTATUSEX   GlobalMemoryStatusEx  amp memInfo   DWORDLONG totalVirtualMem   memInfo ullTotalPageFile   Note  The name  quot TotalPageFile quot  is a bit misleading here  In reality this parameter gives the  quot Virtual Memory Size quot   which is size of swap file plus installed RAM   Virtual Memory currently used  Same code as in  quot Total Virtual Memory quot  and then  DWORDLONG virtualMemUsed   memInfo ullTotalPageFile - memInfo ullAvailPageFile    Virtual Memory currently used by current process   include  quot windows h quot   include  quot psapi h quot   PROCESS MEMORY COUNTERS EX pmc  GetProcessMemoryInfo GetCurrentProcess     PROCESS MEMORY COUNTERS   amp pmc  sizeof pmc    SIZE T virtualMemUsedByMe   pmc PrivateUsage       Total Physical Memory  RAM   Same code as in  quot Total Virtual Memory quot  and then DWORDLONG totalPhysMem   memInfo ullTotalPhys    Physical Memory currently used  Same code as in  quot Total Virtual Memory quot  and then DWORDLONG physMemUsed   memInfo ullTotalPhys - memInfo ullAvailPhys    Physical Memory currently used by current process  Same code as in  quot Virtual Memory currently used by current process quot  and then SIZE T physMemUsedByMe   pmc WorkingSetSize       CPU currently used   include  quot TCHAR h quot   include  quot pdh h quot   static PDH HQUERY cpuQuery  static PDH HCOUNTER cpuTotal   void init        PdhOpenQuery NULL  NULL   amp cpuQuery          You can also use L quot   Processor       Processor Time quot  and get individual CPU values with PdhGetFormattedCounterArray       PdhAddEnglishCounter cpuQuery  L quot   Processor  Total     Processor Time quot   NULL   amp cpuTotal       PdhCollectQueryData cpuQuery      double getCurrentValue        PDH FMT COUNTERVALUE counterVal       PdhCollectQueryData cpuQuery       PdhGetFormattedCounterValue cpuTotal  PDH FMT DOUBLE  NULL   amp counterVal       return counterVal doubleValue      CPU currently used by current process   include  quot windows h quot   static ULARGE INTEGER lastCPU  lastSysCPU  lastUserCPU  static int numProcessors  static HANDLE self   void init        SYSTEM INFO sysInfo      FILETIME ftime  fsys  fuser       GetSystemInfo  amp sysInfo       numProcessors   sysInfo dwNumberOfProcessors       GetSystemTimeAsFileTime  amp ftime       memcpy  amp lastCPU   amp ftime  sizeof FILETIME         self   GetCurrentProcess        GetProcessTimes self   amp ftime   amp ftime   amp fsys   amp fuser       memcpy  amp lastSysCPU   amp fsys  sizeof FILETIME        memcpy  amp lastUserCPU   amp fuser  sizeof FILETIME       double getCurrentValue        FILETIME ftime  fsys  fuser      ULARGE INTEGER now  sys  user      double percent       GetSystemTimeAsFileTime  amp ftime       memcpy  amp now   amp ftime  sizeof FILETIME         GetProcessTimes self   amp ftime   amp ftime   amp fsys   amp fuser       memcpy  amp sys   amp fsys  sizeof FILETIME        memcpy  amp user   amp 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  quot sys types h quot   include  quot sys sysinfo h quot   struct sysinfo memInfo   sysinfo   amp 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  quot Total Virtual Memory quot  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  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   int parseLine char  line          This assumes that a digit will be found and the line ends in  quot  Kb quot       int i   strlen line       const char  p   line      while   p  lt  0      p  gt   9   p        line i-3      0       i   atoi p       return i     int getValue      Note  this value is in KB      FILE  file   fopen  quot  proc self status quot    quot r quot        int result   -1      char line 128        while  fgets line  128  file     NULL           if  strncmp line   quot VmSize  quot   7     0               result   parseLine line               break                      fclose file       return result         Total Physical Memory  RAM   Same code as in  quot Total Virtual Memory quot  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  quot Total Virtual Memory quot  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  quot Virtual Memory currently used by current process quot  as follows  int getValue      Note  this value is in KB      FILE  file   fopen  quot  proc self status quot    quot r quot        int result   -1      char line 128        while  fgets line  128  file     NULL           if  strncmp line   quot VmRSS  quot   6     0               result   parseLine line               break                      fclose file       return result          CPU currently used   include  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   static unsigned long long lastTotalUser  lastTotalUserLow  lastTotalSys  lastTotalIdle   void init        FILE  file   fopen  quot  proc stat quot    quot r quot        fscanf file   quot cpu  llu  llu  llu  llu quot    amp lastTotalUser   amp lastTotalUserLow           amp lastTotalSys   amp lastTotalIdle       fclose file      double getCurrentValue        double percent      FILE  file      unsigned long long totalUser  totalUserLow  totalSys  totalIdle  total       file   fopen  quot  proc stat quot    quot r quot        fscanf file   quot cpu  llu  llu  llu  llu quot    amp totalUser   amp totalUserLow           amp totalSys   amp totalIdle       fclose file        if  totalUser  lt  lastTotalUser    totalUserLow  lt  lastTotalUserLow            totalSys  lt  lastTotalSys    totalIdle  lt  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  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   include  quot sys times h quot   include  quot sys vtimes h quot   static clock t lastCPU  lastSysCPU  lastUserCPU  static int numProcessors   void init        FILE  file      struct tms timeSample      char line 128        lastCPU   times  amp timeSample       lastSysCPU   timeSample tms stime      lastUserCPU   timeSample tms utime       file   fopen  quot  proc cpuinfo quot    quot r quot        numProcessors   0      while fgets line  128  file     NULL           if  strncmp line   quot processor quot   9     0  numProcessors              fclose file      double getCurrentValue        struct tms timeSample      clock t now      double percent       now   times  amp timeSample       if  now  lt   lastCPU    timeSample tms stime  lt  lastSysCPU            timeSample tms utime  lt  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        TODO  Other Platforms I would assume  that some of the Linux code also works for the Unixes  except for the parts that read the  proc pseudo-filesystem  Perhaps on Unix these parts can be replaced by getrusage   and similar functions  If someone with Unix know-how could edit this answer and fill in the details

User · Answer

QNX Since this is like a  quot wikipage of code quot  I want to add some code from the QNX Knowledge base  note  this is not my work  but I checked it and it works fine on my system   How to get CPU usage in    http   www qnx com support knowledgebase html id 50130000000P9b5  include  lt atomic h gt   include  lt libc h gt   include  lt pthread h gt   include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt   include  lt sys iofunc h gt   include  lt sys neutrino h gt   include  lt sys resmgr h gt   include  lt sys syspage h gt   include  lt unistd h gt   include  lt inttypes h gt   include  lt stdio h gt   include  lt stdlib h gt   include  lt unistd h gt   include  lt sys types h gt   include  lt sys debug h gt   include  lt sys procfs h gt   include  lt sys syspage h gt   include  lt sys neutrino h gt   include  lt sys time h gt   include  lt time h gt   include  lt fcntl h gt   include  lt devctl h gt   include  lt errno h gt    define MAX CPUS 32  static float Loads MAX CPUS   static  uint64 LastSutime MAX CPUS   static  uint64 LastNsec MAX CPUS   static int ProcFd   -1  static int NumCpus   0    int find ncpus void        return NumCpus     int get cpu int cpu        int ret      ret    int Loads  cpu   MAX CPUS        ret   max 0 ret       ret   min 100 ret       return  ret       static  uint64 nanoseconds  void          uint64 sec  usec      struct timeval tval      gettimeofday   amp tval  NULL        sec   tval tv sec      usec   tval tv usec      return      sec   1000000     usec     1000       int sample cpus  void         int i      debug thread t debug data       uint64 current nsec  sutime delta  time delta      memset   amp debug data  0  sizeof  debug data               for  i 0  i lt NumCpus  i                  Get the sutime of the idle thread  i 1            debug data tid   i   1          devctl  ProcFd  DCMD PROC TIDSTATUS           amp debug data  sizeof  debug data    NULL               Get the current time            current nsec   nanoseconds               Get the deltas between now and the last samples            sutime delta   debug data sutime - LastSutime i           time delta   current nsec - LastNsec i              Figure out the load            Loads i    100 0 -    float   sutime delta   100      float time delta               Flat out strange rounding issues             if  Loads i   lt  0                 Loads i    0                       Keep these for reference in the next cycle            LastNsec i    current nsec          LastSutime i    debug data sutime            return EOK     int init cpu  void         int i      debug thread t debug data      memset   amp debug data  0  sizeof  debug data         Open a connection to proc to talk over        ProcFd   open   quot  proc 1 as quot   O RDONLY        if  ProcFd    -1             fprintf  stderr   quot pload  Unable to access procnto   s n quot  strerror  errno              fflush  stderr            return -1            i   fcntl ProcFd F GETFD       if i    -1           i    FD CLOEXEC          if fcntl ProcFd F SETFD i     -1                  Grab this value                NumCpus    syspage ptr- gt num cpu                 Get a starting point for the comparisons                for  i 0  i lt NumCpus  i                                            the sutime of idle thread is how much                   time that thread has been using  we can compare this                   against how much time has passed to get an idea of the                   load on the system                                     debug data tid   i   1                  devctl  ProcFd  DCMD PROC TIDSTATUS   amp debug data  sizeof  debug data    NULL                    LastSutime i    debug data sutime                  LastNsec i    nanoseconds                              return EOK                       close ProcFd       return -1      void close cpu void       if ProcFd    -1           close ProcFd           ProcFd   -1           int main int argc  char  argv         int i j      init cpu        printf  quot System has   d CPUs n quot   NumCpus       for i 0  i lt 20  i              sample cpus            for j 0  j lt NumCpus j            printf  quot CPU   d   f n quot   j  Loads j            sleep 1             close cpu       How to get the free     memory  http   www qnx com support knowledgebase html id 50130000000mlbx  include  lt stdio h gt   include  lt stdlib h gt   include  lt errno h gt   include  lt err h gt   include  lt sys stat h gt   include  lt sys types h gt   int main  int argc  char  argv          struct stat statbuf      paddr t freemem      stat   quot  proc quot    amp statbuf        freemem    paddr t statbuf st size      printf   quot Free memory   d bytes n quot   freemem        printf   quot Free memory   d KB n quot   freemem   1024        printf   quot Free memory   d MB n quot   freemem     1024   1024          return 0

User · Answer

Linux  In Linux  this information is available in the  proc file system   I m not a big fan of the text file format used  as each Linux distribution seems to customize at least one important file   A quick look as the source to  ps  reveals the mess   But here is where to find the information you seek    proc meminfo contains the majority of the system-wide information you seek   Here it looks like on my system  I think you are interested in MemTotal  MemFree  SwapTotal  and SwapFree   Anderson cxc   more  proc meminfo MemTotal       4083948 kB MemFree        2198520 kB Buffers          82080 kB Cached         1141460 kB SwapCached           0 kB Active         1137960 kB Inactive        608588 kB HighTotal      3276672 kB HighFree       1607744 kB LowTotal        807276 kB LowFree         590776 kB SwapTotal      2096440 kB SwapFree       2096440 kB Dirty               32 kB Writeback            0 kB AnonPages       523252 kB Mapped           93560 kB Slab             52880 kB SReclaimable     24652 kB SUnreclaim       28228 kB PageTables        2284 kB NFS Unstable         0 kB Bounce               0 kB CommitLimit    4138412 kB Committed AS   1845072 kB VmallocTotal    118776 kB VmallocUsed       3964 kB VmallocChunk    112860 kB HugePages Total      0 HugePages Free       0 HugePages Rsvd       0 Hugepagesize      2048 kB   For CPU utilization  you have to do a little work   Linux makes available overall CPU utilization since system start  this probably isn t what you are interested in   If you want to know what the CPU utilization was for the last second  or 10 seconds  then you need to query the information and calculate it yourself   The information is available in  proc stat  which is documented pretty well at http   www linuxhowtos org System procstat htm  here is what it looks like on my 4-core box   Anderson cxc    more  proc stat cpu  2329889 0 2364567 1063530460 9034 9463 96111 0 cpu0 572526 0 636532 265864398 2928 1621 6899 0 cpu1 590441 0 531079 265949732 4763 351 8522 0 cpu2 562983 0 645163 265796890 682 7490 71650 0 cpu3 603938 0 551790 265919440 660 0 9040 0 intr 37124247 ctxt 50795173133 btime 1218807985 processes 116889 procs running 1 procs blocked 0   First  you need to determine how many CPUs  or processors  or processing cores  are available in the system   To do this  count the number of  cpuN  entries  where N starts at 0 and increments   Don t count the  cpu  line  which is a combination of the cpuN lines   In my example  you can see cpu0 through cpu3  for a total of 4 processors   From now on  you can ignore cpu0  cpu3  and focus only on the  cpu  line   Next  you need to know that the fourth number in these lines is a measure of idle time  and thus the fourth number on the  cpu  line is the total idle time for all processors since boot time   This time is measured in Linux  jiffies   which are 1 100 of a second each    But you don t care about the total idle time  you care about the idle time in a given period  e g   the last second   Do calculate that  you need to read this file twice  1 second apart Then you can do a diff of the fourth value of the line   For example  if you take a sample and get   cpu  2330047 0 2365006 1063853632 9035 9463 96114 0   Then one second later you get this sample   cpu  2330047 0 2365007 1063854028 9035 9463 96114 0   Subtract the two numbers  and you get a diff of 396  which means that your CPU had been idle for 3 96 seconds out of the last 1 00 second   The trick  of course  is that you need to divide by the number of processors   3 96   4   0 99  and there is your idle percentage  99  idle  and 1  busy   In my code  I have a ring buffer of 360 entries  and I read this file every second   That lets me quickly calculate the CPU utilization for 1 second  10 seconds  etc   all the way up to 1 hour   For the process-specific information  you have to look in  proc pid  if you don t care abut your pid  you can look in  proc self   CPU used by your process is available in  proc self stat   This is an odd-looking file consisting of a single line  for example   19340  whatever  S 19115 19115 3084 34816 19115 4202752 118200 607 0 0 770 384 2  7 20 0 77 0 266764385 692477952 105074 4294967295 134512640 146462952 321468364 8 3214683328 4294960144 0 2147221247 268439552 1276 4294967295 0 0 17 0 0 0 0   The important data here are the 13th and 14th tokens  0 and 770 here    The 13th token is the number of jiffies that the process has executed in user mode  and the 14th is the number of jiffies that the process has executed in kernel mode   Add the two together  and you have its total CPU utilization   Again  you will have to sample this file periodically  and calculate the diff  in order to determine the process s CPU usage over time     Edit   remember that when you calculate your process s CPU utilization  you have to take into account 1  the number of threads in your process  and 2  the number of processors in the system   For example  if your single-threaded process is using only 25  of the CPU  that could be good or bad   Good on a single-processor system  but bad on a 4-processor system  this means that your process is running constantly  and using 100  of the CPU cycles available to it   For the process-specific memory information  you ahve to look at  proc self status  which looks like this   Name    whatever State   S  sleeping  Tgid    19340 Pid     19340 PPid    19115 TracerPid       0 Uid     0       0       0       0 Gid     0       0       0       0 FDSize  256 Groups  0 1 2 3 4 6 10 11 20 26 27 VmPeak    676252 kB VmSize    651352 kB VmLck          0 kB VmHWM     420300 kB VmRSS     420296 kB VmData    581028 kB VmStk        112 kB VmExe      11672 kB VmLib      76608 kB VmPTE       1244 kB Threads         77 SigQ    0 36864 SigPnd  0000000000000000 ShdPnd  0000000000000000 SigBlk  fffffffe7ffbfeff SigIgn  0000000010001000 SigCgt  20000001800004fc CapInh  0000000000000000 CapPrm  00000000ffffffff CapEff  00000000fffffeff Cpus allowed    0f Mems allowed    1 voluntary ctxt switches         6518 nonvoluntary ctxt switches      6598   The entries that start with  Vm  are the interesting ones    VmPeak is the maximum virtual memory space used by the process  in kB  1024 bytes   VmSize is the current virtual memory space used by the process  in kB   In my example  it s pretty large   651 352 kB  or about 636 megabytes  VmRss is the amount of memory that have been mapped into the process  address space  or its resident set size   This is substantially smaller  420 296 kB  or about 410 megabytes    The difference   my program has mapped 636 MB via mmap    but has only accessed 410 MB of it  and thus only 410 MB of pages have been assigned to it    The only item I m not sure about is Swapspace currently used by my process   I don t know if this is available

User · Answer

Mac OS X  I was hoping to find similar information for Mac OS X as well  Since it wasn t here  I went out and dug it up myself  Here are some of the things I found  If anyone has any other suggestions  I d love to hear them   Total Virtual Memory  This one is tricky on Mac OS X because it doesn t use a preset swap partition or file like Linux  Here s an entry from Apple s documentation      Note  Unlike most Unix-based operating systems  Mac OS X does not use a preallocated swap partition for virtual memory  Instead  it uses all of the available space on the machine   s boot partition    So  if you want to know how much virtual memory is still available  you need to get the size of the root partition  You can do that like this   struct statfs stats  if  0    statfs       amp stats         myFreeSwap    uint64 t stats f bsize   stats f bfree      Total Virtual Currently Used  Calling systcl with the  vm swapusage  key provides interesting information about swap usage   sysctl -n vm swapusage vm swapusage  total   3072 00M  used   2511 78M  free   560 22M   encrypted    Not that the total swap usage displayed here can change if more swap is needed as explained in the section above  So the total is actually the current swap total  In C    this data can be queried this way   xsw usage vmusage    0   size t size   sizeof vmusage   if  sysctlbyname  vm swapusage    amp vmusage   amp size  NULL  0   0        perror   unable to get swap usage by calling sysctlbyname   vm swapusage                Note that the  xsw usage   declared in sysctl h  seems not documented and I suspect there there is a more portable way of accessing these values   Virtual Memory Currently Used by my Process  You can get statistics about your current process using the task info function  That includes the current resident size of your process and the current virtual size    include lt mach mach h gt   struct task basic info t info  mach msg type number t t info count   TASK BASIC INFO COUNT   if  KERN SUCCESS    task info mach task self                                  TASK BASIC INFO   task info t  amp t info                                  amp t info count         return -1       resident size is in t info resident size     virtual size is in t info virtual size    Total RAM available  The amount of physical RAM available in your system is available using the sysctl system function like this    include  lt sys types h gt   include  lt sys sysctl h gt      int mib 2   int64 t physical memory  mib 0    CTL HW  mib 1    HW MEMSIZE  length   sizeof int64 t   sysctl mib  2   amp physical memory   amp length  NULL  0     RAM Currently Used  You can get general memory statistics from the host statistics system function    include  lt mach vm statistics h gt   include  lt mach mach types h gt   include  lt mach mach init h gt   include  lt mach mach host h gt   int main int argc  const char   argv          vm size t page size      mach port t mach port      mach msg type number t count      vm statistics64 data t vm stats       mach port   mach host self        count   sizeof vm stats    sizeof natural t       if  KERN SUCCESS    host page size mach port   amp page size   amp  amp          KERN SUCCESS    host statistics64 mach port  HOST VM INFO                                           host info64 t  amp vm stats   amp count                 long long free memory    int64 t vm stats free count    int64 t page size           long long used memory     int64 t vm stats active count                                     int64 t vm stats inactive count                                     int64 t vm stats wire count      int64 t page size          printf  free memory   lld nused memory   lld n   free memory  used memory              return 0      One thing to note here are that there are five types of memory pages in Mac OS X  They are as follows    Wired pages that are locked in place and cannot be swapped out Active pages that are loading into physical memory and would be relatively difficult to swap out Inactive pages that are loaded into memory  but haven t been used recently and may not even be needed at all  These are potential candidates for swapping  This memory would probably need to be flushed  Cached pages that have been some how cached that are likely to be easily reused  Cached memory probably would not require flushing  It is still possible for cached pages to be reactivated Free pages that are completely free and ready to be used    It is good to note that just because Mac OS X may show very little actual free memory at times that it may not be a good indication of how much is ready to be used on short notice   RAM Currently Used by my Process  See the  Virtual Memory Currently Used by my Process  above  The same code applies

User · Answer

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 library  PDH   which is a bit  quot unintuitive quot  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  quot windows h quot   MEMORYSTATUSEX memInfo  memInfo dwLength   sizeof MEMORYSTATUSEX   GlobalMemoryStatusEx  amp memInfo   DWORDLONG totalVirtualMem   memInfo ullTotalPageFile   Note  The name  quot TotalPageFile quot  is a bit misleading here  In reality this parameter gives the  quot Virtual Memory Size quot   which is size of swap file plus installed RAM   Virtual Memory currently used  Same code as in  quot Total Virtual Memory quot  and then  DWORDLONG virtualMemUsed   memInfo ullTotalPageFile - memInfo ullAvailPageFile    Virtual Memory currently used by current process   include  quot windows h quot   include  quot psapi h quot   PROCESS MEMORY COUNTERS EX pmc  GetProcessMemoryInfo GetCurrentProcess     PROCESS MEMORY COUNTERS   amp pmc  sizeof pmc    SIZE T virtualMemUsedByMe   pmc PrivateUsage       Total Physical Memory  RAM   Same code as in  quot Total Virtual Memory quot  and then DWORDLONG totalPhysMem   memInfo ullTotalPhys    Physical Memory currently used  Same code as in  quot Total Virtual Memory quot  and then DWORDLONG physMemUsed   memInfo ullTotalPhys - memInfo ullAvailPhys    Physical Memory currently used by current process  Same code as in  quot Virtual Memory currently used by current process quot  and then SIZE T physMemUsedByMe   pmc WorkingSetSize       CPU currently used   include  quot TCHAR h quot   include  quot pdh h quot   static PDH HQUERY cpuQuery  static PDH HCOUNTER cpuTotal   void init        PdhOpenQuery NULL  NULL   amp cpuQuery          You can also use L quot   Processor       Processor Time quot  and get individual CPU values with PdhGetFormattedCounterArray       PdhAddEnglishCounter cpuQuery  L quot   Processor  Total     Processor Time quot   NULL   amp cpuTotal       PdhCollectQueryData cpuQuery      double getCurrentValue        PDH FMT COUNTERVALUE counterVal       PdhCollectQueryData cpuQuery       PdhGetFormattedCounterValue cpuTotal  PDH FMT DOUBLE  NULL   amp counterVal       return counterVal doubleValue      CPU currently used by current process   include  quot windows h quot   static ULARGE INTEGER lastCPU  lastSysCPU  lastUserCPU  static int numProcessors  static HANDLE self   void init        SYSTEM INFO sysInfo      FILETIME ftime  fsys  fuser       GetSystemInfo  amp sysInfo       numProcessors   sysInfo dwNumberOfProcessors       GetSystemTimeAsFileTime  amp ftime       memcpy  amp lastCPU   amp ftime  sizeof FILETIME         self   GetCurrentProcess        GetProcessTimes self   amp ftime   amp ftime   amp fsys   amp fuser       memcpy  amp lastSysCPU   amp fsys  sizeof FILETIME        memcpy  amp lastUserCPU   amp fuser  sizeof FILETIME       double getCurrentValue        FILETIME ftime  fsys  fuser      ULARGE INTEGER now  sys  user      double percent       GetSystemTimeAsFileTime  amp ftime       memcpy  amp now   amp ftime  sizeof FILETIME         GetProcessTimes self   amp ftime   amp ftime   amp fsys   amp fuser       memcpy  amp sys   amp fsys  sizeof FILETIME        memcpy  amp user   amp 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  quot sys types h quot   include  quot sys sysinfo h quot   struct sysinfo memInfo   sysinfo   amp 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  quot Total Virtual Memory quot  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  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   int parseLine char  line          This assumes that a digit will be found and the line ends in  quot  Kb quot       int i   strlen line       const char  p   line      while   p  lt  0      p  gt   9   p        line i-3      0       i   atoi p       return i     int getValue      Note  this value is in KB      FILE  file   fopen  quot  proc self status quot    quot r quot        int result   -1      char line 128        while  fgets line  128  file     NULL           if  strncmp line   quot VmSize  quot   7     0               result   parseLine line               break                      fclose file       return result         Total Physical Memory  RAM   Same code as in  quot Total Virtual Memory quot  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  quot Total Virtual Memory quot  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  quot Virtual Memory currently used by current process quot  as follows  int getValue      Note  this value is in KB      FILE  file   fopen  quot  proc self status quot    quot r quot        int result   -1      char line 128        while  fgets line  128  file     NULL           if  strncmp line   quot VmRSS  quot   6     0               result   parseLine line               break                      fclose file       return result          CPU currently used   include  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   static unsigned long long lastTotalUser  lastTotalUserLow  lastTotalSys  lastTotalIdle   void init        FILE  file   fopen  quot  proc stat quot    quot r quot        fscanf file   quot cpu  llu  llu  llu  llu quot    amp lastTotalUser   amp lastTotalUserLow           amp lastTotalSys   amp lastTotalIdle       fclose file      double getCurrentValue        double percent      FILE  file      unsigned long long totalUser  totalUserLow  totalSys  totalIdle  total       file   fopen  quot  proc stat quot    quot r quot        fscanf file   quot cpu  llu  llu  llu  llu quot    amp totalUser   amp totalUserLow           amp totalSys   amp totalIdle       fclose file        if  totalUser  lt  lastTotalUser    totalUserLow  lt  lastTotalUserLow            totalSys  lt  lastTotalSys    totalIdle  lt  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  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   include  quot sys times h quot   include  quot sys vtimes h quot   static clock t lastCPU  lastSysCPU  lastUserCPU  static int numProcessors   void init        FILE  file      struct tms timeSample      char line 128        lastCPU   times  amp timeSample       lastSysCPU   timeSample tms stime      lastUserCPU   timeSample tms utime       file   fopen  quot  proc cpuinfo quot    quot r quot        numProcessors   0      while fgets line  128  file     NULL           if  strncmp line   quot processor quot   9     0  numProcessors              fclose file      double getCurrentValue        struct tms timeSample      clock t now      double percent       now   times  amp timeSample       if  now  lt   lastCPU    timeSample tms stime  lt  lastSysCPU            timeSample tms utime  lt  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        TODO  Other Platforms I would assume  that some of the Linux code also works for the Unixes  except for the parts that read the  proc pseudo-filesystem  Perhaps on Unix these parts can be replaced by getrusage   and similar functions  If someone with Unix know-how could edit this answer and fill in the details

User · Answer

Mac OS X - CPU  Overall CPU usage   From Retrieve system information on MacOS X      include  lt mach mach init h gt   include  lt mach mach error h gt   include  lt mach mach host h gt   include  lt mach vm map h gt   static unsigned long long  previousTotalTicks   0  static unsigned long long  previousIdleTicks   0      Returns 1 0f for  CPU fully pinned   0 0f for  CPU idle   or somewhere in between    You ll need to call this at regular intervals  since it measures the load between    the previous call and the current one  float GetCPULoad        host cpu load info data t cpuinfo     mach msg type number t count   HOST CPU LOAD INFO COUNT     if  host statistics mach host self    HOST CPU LOAD INFO   host info t  amp cpuinfo   amp count     KERN SUCCESS             unsigned long long totalTicks   0        for int i 0  i lt CPU STATE MAX  i    totalTicks    cpuinfo cpu ticks i         return CalculateCPULoad cpuinfo cpu ticks CPU STATE IDLE   totalTicks           else return -1 0f     float CalculateCPULoad unsigned long long idleTicks  unsigned long long totalTicks      unsigned long long totalTicksSinceLastTime   totalTicks- previousTotalTicks    unsigned long long idleTicksSinceLastTime    idleTicks- previousIdleTicks    float ret   1 0f-  totalTicksSinceLastTime  gt  0      float idleTicksSinceLastTime  totalTicksSinceLastTime   0      previousTotalTicks   totalTicks     previousIdleTicks    idleTicks    return ret

User · Answer

in windows you can get cpu usage by code bellow    include  lt windows h gt   include  lt stdio h gt         ------------------------------------------------------------------------------------------------------------------        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 on C language            add this line    pfnGetSystemTimes            s pfnGetSystemTimes  amp ft sys idle        System idle time                 amp ft sys kernel      system kernel time                 amp ft sys user        System user time             CopyMemory  amp ul sys idle     amp ft sys idle    sizeof FILETIME       Could been optimized away            CopyMemory  amp ul sys kernel   amp ft sys kernel  sizeof FILETIME       Could been optimized away            CopyMemory  amp ul sys user     amp 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 lt 20 n                          printf  CPU Usage   3d   r  cpuusage                 Sleep 2000                     printf   n            return 0

User · Answer

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 library  PDH   which is a bit  quot unintuitive quot  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  quot windows h quot   MEMORYSTATUSEX memInfo  memInfo dwLength   sizeof MEMORYSTATUSEX   GlobalMemoryStatusEx  amp memInfo   DWORDLONG totalVirtualMem   memInfo ullTotalPageFile   Note  The name  quot TotalPageFile quot  is a bit misleading here  In reality this parameter gives the  quot Virtual Memory Size quot   which is size of swap file plus installed RAM   Virtual Memory currently used  Same code as in  quot Total Virtual Memory quot  and then  DWORDLONG virtualMemUsed   memInfo ullTotalPageFile - memInfo ullAvailPageFile    Virtual Memory currently used by current process   include  quot windows h quot   include  quot psapi h quot   PROCESS MEMORY COUNTERS EX pmc  GetProcessMemoryInfo GetCurrentProcess     PROCESS MEMORY COUNTERS   amp pmc  sizeof pmc    SIZE T virtualMemUsedByMe   pmc PrivateUsage       Total Physical Memory  RAM   Same code as in  quot Total Virtual Memory quot  and then DWORDLONG totalPhysMem   memInfo ullTotalPhys    Physical Memory currently used  Same code as in  quot Total Virtual Memory quot  and then DWORDLONG physMemUsed   memInfo ullTotalPhys - memInfo ullAvailPhys    Physical Memory currently used by current process  Same code as in  quot Virtual Memory currently used by current process quot  and then SIZE T physMemUsedByMe   pmc WorkingSetSize       CPU currently used   include  quot TCHAR h quot   include  quot pdh h quot   static PDH HQUERY cpuQuery  static PDH HCOUNTER cpuTotal   void init        PdhOpenQuery NULL  NULL   amp cpuQuery          You can also use L quot   Processor       Processor Time quot  and get individual CPU values with PdhGetFormattedCounterArray       PdhAddEnglishCounter cpuQuery  L quot   Processor  Total     Processor Time quot   NULL   amp cpuTotal       PdhCollectQueryData cpuQuery      double getCurrentValue        PDH FMT COUNTERVALUE counterVal       PdhCollectQueryData cpuQuery       PdhGetFormattedCounterValue cpuTotal  PDH FMT DOUBLE  NULL   amp counterVal       return counterVal doubleValue      CPU currently used by current process   include  quot windows h quot   static ULARGE INTEGER lastCPU  lastSysCPU  lastUserCPU  static int numProcessors  static HANDLE self   void init        SYSTEM INFO sysInfo      FILETIME ftime  fsys  fuser       GetSystemInfo  amp sysInfo       numProcessors   sysInfo dwNumberOfProcessors       GetSystemTimeAsFileTime  amp ftime       memcpy  amp lastCPU   amp ftime  sizeof FILETIME         self   GetCurrentProcess        GetProcessTimes self   amp ftime   amp ftime   amp fsys   amp fuser       memcpy  amp lastSysCPU   amp fsys  sizeof FILETIME        memcpy  amp lastUserCPU   amp fuser  sizeof FILETIME       double getCurrentValue        FILETIME ftime  fsys  fuser      ULARGE INTEGER now  sys  user      double percent       GetSystemTimeAsFileTime  amp ftime       memcpy  amp now   amp ftime  sizeof FILETIME         GetProcessTimes self   amp ftime   amp ftime   amp fsys   amp fuser       memcpy  amp sys   amp fsys  sizeof FILETIME        memcpy  amp user   amp 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  quot sys types h quot   include  quot sys sysinfo h quot   struct sysinfo memInfo   sysinfo   amp 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  quot Total Virtual Memory quot  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  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   int parseLine char  line          This assumes that a digit will be found and the line ends in  quot  Kb quot       int i   strlen line       const char  p   line      while   p  lt  0      p  gt   9   p        line i-3      0       i   atoi p       return i     int getValue      Note  this value is in KB      FILE  file   fopen  quot  proc self status quot    quot r quot        int result   -1      char line 128        while  fgets line  128  file     NULL           if  strncmp line   quot VmSize  quot   7     0               result   parseLine line               break                      fclose file       return result         Total Physical Memory  RAM   Same code as in  quot Total Virtual Memory quot  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  quot Total Virtual Memory quot  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  quot Virtual Memory currently used by current process quot  as follows  int getValue      Note  this value is in KB      FILE  file   fopen  quot  proc self status quot    quot r quot        int result   -1      char line 128        while  fgets line  128  file     NULL           if  strncmp line   quot VmRSS  quot   6     0               result   parseLine line               break                      fclose file       return result          CPU currently used   include  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   static unsigned long long lastTotalUser  lastTotalUserLow  lastTotalSys  lastTotalIdle   void init        FILE  file   fopen  quot  proc stat quot    quot r quot        fscanf file   quot cpu  llu  llu  llu  llu quot    amp lastTotalUser   amp lastTotalUserLow           amp lastTotalSys   amp lastTotalIdle       fclose file      double getCurrentValue        double percent      FILE  file      unsigned long long totalUser  totalUserLow  totalSys  totalIdle  total       file   fopen  quot  proc stat quot    quot r quot        fscanf file   quot cpu  llu  llu  llu  llu quot    amp totalUser   amp totalUserLow           amp totalSys   amp totalIdle       fclose file        if  totalUser  lt  lastTotalUser    totalUserLow  lt  lastTotalUserLow            totalSys  lt  lastTotalSys    totalIdle  lt  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  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   include  quot sys times h quot   include  quot sys vtimes h quot   static clock t lastCPU  lastSysCPU  lastUserCPU  static int numProcessors   void init        FILE  file      struct tms timeSample      char line 128        lastCPU   times  amp timeSample       lastSysCPU   timeSample tms stime      lastUserCPU   timeSample tms utime       file   fopen  quot  proc cpuinfo quot    quot r quot        numProcessors   0      while fgets line  128  file     NULL           if  strncmp line   quot processor quot   9     0  numProcessors              fclose file      double getCurrentValue        struct tms timeSample      clock t now      double percent       now   times  amp timeSample       if  now  lt   lastCPU    timeSample tms stime  lt  lastSysCPU            timeSample tms utime  lt  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        TODO  Other Platforms I would assume  that some of the Linux code also works for the Unixes  except for the parts that read the  proc pseudo-filesystem  Perhaps on Unix these parts can be replaced by getrusage   and similar functions  If someone with Unix know-how could edit this answer and fill in the details

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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 library  PDH   which is a bit  quot unintuitive quot  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  quot windows h quot   MEMORYSTATUSEX memInfo  memInfo dwLength   sizeof MEMORYSTATUSEX   GlobalMemoryStatusEx  amp memInfo   DWORDLONG totalVirtualMem   memInfo ullTotalPageFile   Note  The name  quot TotalPageFile quot  is a bit misleading here  In reality this parameter gives the  quot Virtual Memory Size quot   which is size of swap file plus installed RAM   Virtual Memory currently used  Same code as in  quot Total Virtual Memory quot  and then  DWORDLONG virtualMemUsed   memInfo ullTotalPageFile - memInfo ullAvailPageFile    Virtual Memory currently used by current process   include  quot windows h quot   include  quot psapi h quot   PROCESS MEMORY COUNTERS EX pmc  GetProcessMemoryInfo GetCurrentProcess     PROCESS MEMORY COUNTERS   amp pmc  sizeof pmc    SIZE T virtualMemUsedByMe   pmc PrivateUsage       Total Physical Memory  RAM   Same code as in  quot Total Virtual Memory quot  and then DWORDLONG totalPhysMem   memInfo ullTotalPhys    Physical Memory currently used  Same code as in  quot Total Virtual Memory quot  and then DWORDLONG physMemUsed   memInfo ullTotalPhys - memInfo ullAvailPhys    Physical Memory currently used by current process  Same code as in  quot Virtual Memory currently used by current process quot  and then SIZE T physMemUsedByMe   pmc WorkingSetSize       CPU currently used   include  quot TCHAR h quot   include  quot pdh h quot   static PDH HQUERY cpuQuery  static PDH HCOUNTER cpuTotal   void init        PdhOpenQuery NULL  NULL   amp cpuQuery          You can also use L quot   Processor       Processor Time quot  and get individual CPU values with PdhGetFormattedCounterArray       PdhAddEnglishCounter cpuQuery  L quot   Processor  Total     Processor Time quot   NULL   amp cpuTotal       PdhCollectQueryData cpuQuery      double getCurrentValue        PDH FMT COUNTERVALUE counterVal       PdhCollectQueryData cpuQuery       PdhGetFormattedCounterValue cpuTotal  PDH FMT DOUBLE  NULL   amp counterVal       return counterVal doubleValue      CPU currently used by current process   include  quot windows h quot   static ULARGE INTEGER lastCPU  lastSysCPU  lastUserCPU  static int numProcessors  static HANDLE self   void init        SYSTEM INFO sysInfo      FILETIME ftime  fsys  fuser       GetSystemInfo  amp sysInfo       numProcessors   sysInfo dwNumberOfProcessors       GetSystemTimeAsFileTime  amp ftime       memcpy  amp lastCPU   amp ftime  sizeof FILETIME         self   GetCurrentProcess        GetProcessTimes self   amp ftime   amp ftime   amp fsys   amp fuser       memcpy  amp lastSysCPU   amp fsys  sizeof FILETIME        memcpy  amp lastUserCPU   amp fuser  sizeof FILETIME       double getCurrentValue        FILETIME ftime  fsys  fuser      ULARGE INTEGER now  sys  user      double percent       GetSystemTimeAsFileTime  amp ftime       memcpy  amp now   amp ftime  sizeof FILETIME         GetProcessTimes self   amp ftime   amp ftime   amp fsys   amp fuser       memcpy  amp sys   amp fsys  sizeof FILETIME        memcpy  amp user   amp 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  quot sys types h quot   include  quot sys sysinfo h quot   struct sysinfo memInfo   sysinfo   amp 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  quot Total Virtual Memory quot  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  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   int parseLine char  line          This assumes that a digit will be found and the line ends in  quot  Kb quot       int i   strlen line       const char  p   line      while   p  lt  0      p  gt   9   p        line i-3      0       i   atoi p       return i     int getValue      Note  this value is in KB      FILE  file   fopen  quot  proc self status quot    quot r quot        int result   -1      char line 128        while  fgets line  128  file     NULL           if  strncmp line   quot VmSize  quot   7     0               result   parseLine line               break                      fclose file       return result         Total Physical Memory  RAM   Same code as in  quot Total Virtual Memory quot  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  quot Total Virtual Memory quot  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  quot Virtual Memory currently used by current process quot  as follows  int getValue      Note  this value is in KB      FILE  file   fopen  quot  proc self status quot    quot r quot        int result   -1      char line 128        while  fgets line  128  file     NULL           if  strncmp line   quot VmRSS  quot   6     0               result   parseLine line               break                      fclose file       return result          CPU currently used   include  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   static unsigned long long lastTotalUser  lastTotalUserLow  lastTotalSys  lastTotalIdle   void init        FILE  file   fopen  quot  proc stat quot    quot r quot        fscanf file   quot cpu  llu  llu  llu  llu quot    amp lastTotalUser   amp lastTotalUserLow           amp lastTotalSys   amp lastTotalIdle       fclose file      double getCurrentValue        double percent      FILE  file      unsigned long long totalUser  totalUserLow  totalSys  totalIdle  total       file   fopen  quot  proc stat quot    quot r quot        fscanf file   quot cpu  llu  llu  llu  llu quot    amp totalUser   amp totalUserLow           amp totalSys   amp totalIdle       fclose file        if  totalUser  lt  lastTotalUser    totalUserLow  lt  lastTotalUserLow            totalSys  lt  lastTotalSys    totalIdle  lt  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  quot stdlib h quot   include  quot stdio h quot   include  quot string h quot   include  quot sys times h quot   include  quot sys vtimes h quot   static clock t lastCPU  lastSysCPU  lastUserCPU  static int numProcessors   void init        FILE  file      struct tms timeSample      char line 128        lastCPU   times  amp timeSample       lastSysCPU   timeSample tms stime      lastUserCPU   timeSample tms utime       file   fopen  quot  proc cpuinfo quot    quot r quot        numProcessors   0      while fgets line  128  file     NULL           if  strncmp line   quot processor quot   9     0  numProcessors              fclose file      double getCurrentValue        struct tms timeSample      clock t now      double percent       now   times  amp timeSample       if  now  lt   lastCPU    timeSample tms stime  lt  lastSysCPU            timeSample tms utime  lt  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        TODO  Other Platforms I would assume  that some of the Linux code also works for the Unixes  except for the parts that read the  proc pseudo-filesystem  Perhaps on Unix these parts can be replaced by getrusage   and similar functions  If someone with Unix know-how could edit this answer and fill in the details

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For Linux You can also use  proc self statm to get a single line of numbers containing key process memory information which is a faster thing to process than going through a long list of reported information as you get from proc self status  See http   man7 org linux man-pages man5 proc 5 html      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

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QNX Since this is like a  quot wikipage of code quot  I want to add some code from the QNX Knowledge base  note  this is not my work  but I checked it and it works fine on my system   How to get CPU usage in    http   www qnx com support knowledgebase html id 50130000000P9b5  include  lt atomic h gt   include  lt libc h gt   include  lt pthread h gt   include  lt stdio h gt   include  lt stdlib h gt   include  lt string h gt   include  lt sys iofunc h gt   include  lt sys neutrino h gt   include  lt sys resmgr h gt   include  lt sys syspage h gt   include  lt unistd h gt   include  lt inttypes h gt   include  lt stdio h gt   include  lt stdlib h gt   include  lt unistd h gt   include  lt sys types h gt   include  lt sys debug h gt   include  lt sys procfs h gt   include  lt sys syspage h gt   include  lt sys neutrino h gt   include  lt sys time h gt   include  lt time h gt   include  lt fcntl h gt   include  lt devctl h gt   include  lt errno h gt    define MAX CPUS 32  static float Loads MAX CPUS   static  uint64 LastSutime MAX CPUS   static  uint64 LastNsec MAX CPUS   static int ProcFd   -1  static int NumCpus   0    int find ncpus void        return NumCpus     int get cpu int cpu        int ret      ret    int Loads  cpu   MAX CPUS        ret   max 0 ret       ret   min 100 ret       return  ret       static  uint64 nanoseconds  void          uint64 sec  usec      struct timeval tval      gettimeofday   amp tval  NULL        sec   tval tv sec      usec   tval tv usec      return      sec   1000000     usec     1000       int sample cpus  void         int i      debug thread t debug data       uint64 current nsec  sutime delta  time delta      memset   amp debug data  0  sizeof  debug data               for  i 0  i lt NumCpus  i                  Get the sutime of the idle thread  i 1            debug data tid   i   1          devctl  ProcFd  DCMD PROC TIDSTATUS           amp debug data  sizeof  debug data    NULL               Get the current time            current nsec   nanoseconds               Get the deltas between now and the last samples            sutime delta   debug data sutime - LastSutime i           time delta   current nsec - LastNsec i              Figure out the load            Loads i    100 0 -    float   sutime delta   100      float time delta               Flat out strange rounding issues             if  Loads i   lt  0                 Loads i    0                       Keep these for reference in the next cycle            LastNsec i    current nsec          LastSutime i    debug data sutime            return EOK     int init cpu  void         int i      debug thread t debug data      memset   amp debug data  0  sizeof  debug data         Open a connection to proc to talk over        ProcFd   open   quot  proc 1 as quot   O RDONLY        if  ProcFd    -1             fprintf  stderr   quot pload  Unable to access procnto   s n quot  strerror  errno              fflush  stderr            return -1            i   fcntl ProcFd F GETFD       if i    -1           i    FD CLOEXEC          if fcntl ProcFd F SETFD i     -1                  Grab this value                NumCpus    syspage ptr- gt num cpu                 Get a starting point for the comparisons                for  i 0  i lt NumCpus  i                                            the sutime of idle thread is how much                   time that thread has been using  we can compare this                   against how much time has passed to get an idea of the                   load on the system                                     debug data tid   i   1                  devctl  ProcFd  DCMD PROC TIDSTATUS   amp debug data  sizeof  debug data    NULL                    LastSutime i    debug data sutime                  LastNsec i    nanoseconds                              return EOK                       close ProcFd       return -1      void close cpu void       if ProcFd    -1           close ProcFd           ProcFd   -1           int main int argc  char  argv         int i j      init cpu        printf  quot System has   d CPUs n quot   NumCpus       for i 0  i lt 20  i              sample cpus            for j 0  j lt NumCpus j            printf  quot CPU   d   f n quot   j  Loads j            sleep 1             close cpu       How to get the free     memory  http   www qnx com support knowledgebase html id 50130000000mlbx  include  lt stdio h gt   include  lt stdlib h gt   include  lt errno h gt   include  lt err h gt   include  lt sys stat h gt   include  lt sys types h gt   int main  int argc  char  argv          struct stat statbuf      paddr t freemem      stat   quot  proc quot    amp statbuf        freemem    paddr t statbuf st size      printf   quot Free memory   d bytes n quot   freemem        printf   quot Free memory   d KB n quot   freemem   1024        printf   quot Free memory   d MB n quot   freemem     1024   1024          return 0

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I used this following code in my C   project and it worked fine   static HANDLE self  static int numProcessors  SYSTEM INFO sysInfo   double percent   numProcessors   sysInfo dwNumberOfProcessors     Getting system times information FILETIME SysidleTime  FILETIME SyskernelTime   FILETIME SysuserTime   ULARGE INTEGER SyskernelTimeInt  SysuserTimeInt  GetSystemTimes  amp SysidleTime   amp SyskernelTime   amp SysuserTime   memcpy  amp SyskernelTimeInt   amp SyskernelTime  sizeof FILETIME    memcpy  amp SysuserTimeInt   amp SysuserTime  sizeof FILETIME      int64 denomenator   SysuserTimeInt QuadPart   SyskernelTimeInt QuadPart       Getting process times information FILETIME ProccreationTime  ProcexitTime  ProcKernelTime  ProcUserTime  ULARGE INTEGER ProccreationTimeInt  ProcexitTimeInt  ProcKernelTimeInt  ProcUserTimeInt  GetProcessTimes self   amp ProccreationTime   amp ProcexitTime   amp ProcKernelTime   amp ProcUserTime   memcpy  amp ProcKernelTimeInt   amp ProcKernelTime  sizeof FILETIME    memcpy  amp ProcUserTimeInt   amp ProcUserTime  sizeof FILETIME      int64 numerator   ProcUserTimeInt QuadPart   ProcKernelTimeInt QuadPart    QuadPart represents a 64-bit signed integer  ULARGE INTEGER   percent   100  numerator denomenator

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I used this following code in my C   project and it worked fine   static HANDLE self  static int numProcessors  SYSTEM INFO sysInfo   double percent   numProcessors   sysInfo dwNumberOfProcessors     Getting system times information FILETIME SysidleTime  FILETIME SyskernelTime   FILETIME SysuserTime   ULARGE INTEGER SyskernelTimeInt  SysuserTimeInt  GetSystemTimes  amp SysidleTime   amp SyskernelTime   amp SysuserTime   memcpy  amp SyskernelTimeInt   amp SyskernelTime  sizeof FILETIME    memcpy  amp SysuserTimeInt   amp SysuserTime  sizeof FILETIME      int64 denomenator   SysuserTimeInt QuadPart   SyskernelTimeInt QuadPart       Getting process times information FILETIME ProccreationTime  ProcexitTime  ProcKernelTime  ProcUserTime  ULARGE INTEGER ProccreationTimeInt  ProcexitTimeInt  ProcKernelTimeInt  ProcUserTimeInt  GetProcessTimes self   amp ProccreationTime   amp ProcexitTime   amp ProcKernelTime   amp ProcUserTime   memcpy  amp ProcKernelTimeInt   amp ProcKernelTime  sizeof FILETIME    memcpy  amp ProcUserTimeInt   amp ProcUserTime  sizeof FILETIME      int64 numerator   ProcUserTimeInt QuadPart   ProcKernelTimeInt QuadPart    QuadPart represents a 64-bit signed integer  ULARGE INTEGER   percent   100  numerator denomenator

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Linux  A portable way of reading memory and load numbers is the sysinfo call  Usage      include  lt sys sysinfo h gt      int sysinfo struct sysinfo  info     DESCRIPTION     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

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Mac OS X  I was hoping to find similar information for Mac OS X as well  Since it wasn t here  I went out and dug it up myself  Here are some of the things I found  If anyone has any other suggestions  I d love to hear them   Total Virtual Memory  This one is tricky on Mac OS X because it doesn t use a preset swap partition or file like Linux  Here s an entry from Apple s documentation      Note  Unlike most Unix-based operating systems  Mac OS X does not use a preallocated swap partition for virtual memory  Instead  it uses all of the available space on the machine   s boot partition    So  if you want to know how much virtual memory is still available  you need to get the size of the root partition  You can do that like this   struct statfs stats  if  0    statfs       amp stats         myFreeSwap    uint64 t stats f bsize   stats f bfree      Total Virtual Currently Used  Calling systcl with the  vm swapusage  key provides interesting information about swap usage   sysctl -n vm swapusage vm swapusage  total   3072 00M  used   2511 78M  free   560 22M   encrypted    Not that the total swap usage displayed here can change if more swap is needed as explained in the section above  So the total is actually the current swap total  In C    this data can be queried this way   xsw usage vmusage    0   size t size   sizeof vmusage   if  sysctlbyname  vm swapusage    amp vmusage   amp size  NULL  0   0        perror   unable to get swap usage by calling sysctlbyname   vm swapusage                Note that the  xsw usage   declared in sysctl h  seems not documented and I suspect there there is a more portable way of accessing these values   Virtual Memory Currently Used by my Process  You can get statistics about your current process using the task info function  That includes the current resident size of your process and the current virtual size    include lt mach mach h gt   struct task basic info t info  mach msg type number t t info count   TASK BASIC INFO COUNT   if  KERN SUCCESS    task info mach task self                                  TASK BASIC INFO   task info t  amp t info                                  amp t info count         return -1       resident size is in t info resident size     virtual size is in t info virtual size    Total RAM available  The amount of physical RAM available in your system is available using the sysctl system function like this    include  lt sys types h gt   include  lt sys sysctl h gt      int mib 2   int64 t physical memory  mib 0    CTL HW  mib 1    HW MEMSIZE  length   sizeof int64 t   sysctl mib  2   amp physical memory   amp length  NULL  0     RAM Currently Used  You can get general memory statistics from the host statistics system function    include  lt mach vm statistics h gt   include  lt mach mach types h gt   include  lt mach mach init h gt   include  lt mach mach host h gt   int main int argc  const char   argv          vm size t page size      mach port t mach port      mach msg type number t count      vm statistics64 data t vm stats       mach port   mach host self        count   sizeof vm stats    sizeof natural t       if  KERN SUCCESS    host page size mach port   amp page size   amp  amp          KERN SUCCESS    host statistics64 mach port  HOST VM INFO                                           host info64 t  amp vm stats   amp count                 long long free memory    int64 t vm stats free count    int64 t page size           long long used memory     int64 t vm stats active count                                     int64 t vm stats inactive count                                     int64 t vm stats wire count      int64 t page size          printf  free memory   lld nused memory   lld n   free memory  used memory              return 0      One thing to note here are that there are five types of memory pages in Mac OS X  They are as follows    Wired pages that are locked in place and cannot be swapped out Active pages that are loading into physical memory and would be relatively difficult to swap out Inactive pages that are loaded into memory  but haven t been used recently and may not even be needed at all  These are potential candidates for swapping  This memory would probably need to be flushed  Cached pages that have been some how cached that are likely to be easily reused  Cached memory probably would not require flushing  It is still possible for cached pages to be reactivated Free pages that are completely free and ready to be used    It is good to note that just because Mac OS X may show very little actual free memory at times that it may not be a good indication of how much is ready to be used on short notice   RAM Currently Used by my Process  See the  Virtual Memory Currently Used by my Process  above  The same code applies

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Linux  In Linux  this information is available in the  proc file system   I m not a big fan of the text file format used  as each Linux distribution seems to customize at least one important file   A quick look as the source to  ps  reveals the mess   But here is where to find the information you seek    proc meminfo contains the majority of the system-wide information you seek   Here it looks like on my system  I think you are interested in MemTotal  MemFree  SwapTotal  and SwapFree   Anderson cxc   more  proc meminfo MemTotal       4083948 kB MemFree        2198520 kB Buffers          82080 kB Cached         1141460 kB SwapCached           0 kB Active         1137960 kB Inactive        608588 kB HighTotal      3276672 kB HighFree       1607744 kB LowTotal        807276 kB LowFree         590776 kB SwapTotal      2096440 kB SwapFree       2096440 kB Dirty               32 kB Writeback            0 kB AnonPages       523252 kB Mapped           93560 kB Slab             52880 kB SReclaimable     24652 kB SUnreclaim       28228 kB PageTables        2284 kB NFS Unstable         0 kB Bounce               0 kB CommitLimit    4138412 kB Committed AS   1845072 kB VmallocTotal    118776 kB VmallocUsed       3964 kB VmallocChunk    112860 kB HugePages Total      0 HugePages Free       0 HugePages Rsvd       0 Hugepagesize      2048 kB   For CPU utilization  you have to do a little work   Linux makes available overall CPU utilization since system start  this probably isn t what you are interested in   If you want to know what the CPU utilization was for the last second  or 10 seconds  then you need to query the information and calculate it yourself   The information is available in  proc stat  which is documented pretty well at http   www linuxhowtos org System procstat htm  here is what it looks like on my 4-core box   Anderson cxc    more  proc stat cpu  2329889 0 2364567 1063530460 9034 9463 96111 0 cpu0 572526 0 636532 265864398 2928 1621 6899 0 cpu1 590441 0 531079 265949732 4763 351 8522 0 cpu2 562983 0 645163 265796890 682 7490 71650 0 cpu3 603938 0 551790 265919440 660 0 9040 0 intr 37124247 ctxt 50795173133 btime 1218807985 processes 116889 procs running 1 procs blocked 0   First  you need to determine how many CPUs  or processors  or processing cores  are available in the system   To do this  count the number of  cpuN  entries  where N starts at 0 and increments   Don t count the  cpu  line  which is a combination of the cpuN lines   In my example  you can see cpu0 through cpu3  for a total of 4 processors   From now on  you can ignore cpu0  cpu3  and focus only on the  cpu  line   Next  you need to know that the fourth number in these lines is a measure of idle time  and thus the fourth number on the  cpu  line is the total idle time for all processors since boot time   This time is measured in Linux  jiffies   which are 1 100 of a second each    But you don t care about the total idle time  you care about the idle time in a given period  e g   the last second   Do calculate that  you need to read this file twice  1 second apart Then you can do a diff of the fourth value of the line   For example  if you take a sample and get   cpu  2330047 0 2365006 1063853632 9035 9463 96114 0   Then one second later you get this sample   cpu  2330047 0 2365007 1063854028 9035 9463 96114 0   Subtract the two numbers  and you get a diff of 396  which means that your CPU had been idle for 3 96 seconds out of the last 1 00 second   The trick  of course  is that you need to divide by the number of processors   3 96   4   0 99  and there is your idle percentage  99  idle  and 1  busy   In my code  I have a ring buffer of 360 entries  and I read this file every second   That lets me quickly calculate the CPU utilization for 1 second  10 seconds  etc   all the way up to 1 hour   For the process-specific information  you have to look in  proc pid  if you don t care abut your pid  you can look in  proc self   CPU used by your process is available in  proc self stat   This is an odd-looking file consisting of a single line  for example   19340  whatever  S 19115 19115 3084 34816 19115 4202752 118200 607 0 0 770 384 2  7 20 0 77 0 266764385 692477952 105074 4294967295 134512640 146462952 321468364 8 3214683328 4294960144 0 2147221247 268439552 1276 4294967295 0 0 17 0 0 0 0   The important data here are the 13th and 14th tokens  0 and 770 here    The 13th token is the number of jiffies that the process has executed in user mode  and the 14th is the number of jiffies that the process has executed in kernel mode   Add the two together  and you have its total CPU utilization   Again  you will have to sample this file periodically  and calculate the diff  in order to determine the process s CPU usage over time     Edit   remember that when you calculate your process s CPU utilization  you have to take into account 1  the number of threads in your process  and 2  the number of processors in the system   For example  if your single-threaded process is using only 25  of the CPU  that could be good or bad   Good on a single-processor system  but bad on a 4-processor system  this means that your process is running constantly  and using 100  of the CPU cycles available to it   For the process-specific memory information  you ahve to look at  proc self status  which looks like this   Name    whatever State   S  sleeping  Tgid    19340 Pid     19340 PPid    19115 TracerPid       0 Uid     0       0       0       0 Gid     0       0       0       0 FDSize  256 Groups  0 1 2 3 4 6 10 11 20 26 27 VmPeak    676252 kB VmSize    651352 kB VmLck          0 kB VmHWM     420300 kB VmRSS     420296 kB VmData    581028 kB VmStk        112 kB VmExe      11672 kB VmLib      76608 kB VmPTE       1244 kB Threads         77 SigQ    0 36864 SigPnd  0000000000000000 ShdPnd  0000000000000000 SigBlk  fffffffe7ffbfeff SigIgn  0000000010001000 SigCgt  20000001800004fc CapInh  0000000000000000 CapPrm  00000000ffffffff CapEff  00000000fffffeff Cpus allowed    0f Mems allowed    1 voluntary ctxt switches         6518 nonvoluntary ctxt switches      6598   The entries that start with  Vm  are the interesting ones    VmPeak is the maximum virtual memory space used by the process  in kB  1024 bytes   VmSize is the current virtual memory space used by the process  in kB   In my example  it s pretty large   651 352 kB  or about 636 megabytes  VmRss is the amount of memory that have been mapped into the process  address space  or its resident set size   This is substantially smaller  420 296 kB  or about 410 megabytes    The difference   my program has mapped 636 MB via mmap    but has only accessed 410 MB of it  and thus only 410 MB of pages have been assigned to it    The only item I m not sure about is Swapspace currently used by my process   I don t know if this is available

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On linux  you cannot shouldnot get  quot Total Available Physical Memory quot  with SysInfo s freeram or by doing some arithmetic on totalram  The recommended way to do this is by reading proc meminfo  quoting https   git kernel org pub scm linux kernel git torvalds linux git commit  id 34e431b0ae398fc54ea69ff85ec700722c9da773   Many load balancing and workload placing programs check  proc meminfo to estimate how much free memory is available   They generally do this by adding up  quot free quot  and  quot cached quot   which was fine ten years ago  but is pretty much guaranteed to be wrong today    It is more convenient to provide such an estimate in  proc meminfo   If things change in the future  we only have to change it in one place   One way to do it is as https   stackoverflow com a 350039 7984460 suggest  read the file  and use fscanf to grab the line  but instead of going for MemTotal  go for MemAvailable  Likewise  if you want to get the total amounf of physical memory used  depending on what you mean by  quot use quot   you might not want to subtract freeram from totalram  but subtract memavailable from memtotal to get what top htop tell you

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Mac OS X - CPU  Overall CPU usage   From Retrieve system information on MacOS X      include  lt mach mach init h gt   include  lt mach mach error h gt   include  lt mach mach host h gt   include  lt mach vm map h gt   static unsigned long long  previousTotalTicks   0  static unsigned long long  previousIdleTicks   0      Returns 1 0f for  CPU fully pinned   0 0f for  CPU idle   or somewhere in between    You ll need to call this at regular intervals  since it measures the load between    the previous call and the current one  float GetCPULoad        host cpu load info data t cpuinfo     mach msg type number t count   HOST CPU LOAD INFO COUNT     if  host statistics mach host self    HOST CPU LOAD INFO   host info t  amp cpuinfo   amp count     KERN SUCCESS             unsigned long long totalTicks   0        for int i 0  i lt CPU STATE MAX  i    totalTicks    cpuinfo cpu ticks i         return CalculateCPULoad cpuinfo cpu ticks CPU STATE IDLE   totalTicks           else return -1 0f     float CalculateCPULoad unsigned long long idleTicks  unsigned long long totalTicks      unsigned long long totalTicksSinceLastTime   totalTicks- previousTotalTicks    unsigned long long idleTicksSinceLastTime    idleTicks- previousIdleTicks    float ret   1 0f-  totalTicksSinceLastTime  gt  0      float idleTicksSinceLastTime  totalTicksSinceLastTime   0      previousTotalTicks   totalTicks     previousIdleTicks    idleTicks    return ret

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On linux  you cannot shouldnot get  quot Total Available Physical Memory quot  with SysInfo s freeram or by doing some arithmetic on totalram  The recommended way to do this is by reading proc meminfo  quoting https   git kernel org pub scm linux kernel git torvalds linux git commit  id 34e431b0ae398fc54ea69ff85ec700722c9da773   Many load balancing and workload placing programs check  proc meminfo to estimate how much free memory is available   They generally do this by adding up  quot free quot  and  quot cached quot   which was fine ten years ago  but is pretty much guaranteed to be wrong today    It is more convenient to provide such an estimate in  proc meminfo   If things change in the future  we only have to change it in one place   One way to do it is as https   stackoverflow com a 350039 7984460 suggest  read the file  and use fscanf to grab the line  but instead of going for MemTotal  go for MemAvailable  Likewise  if you want to get the total amounf of physical memory used  depending on what you mean by  quot use quot   you might not want to subtract freeram from totalram  but subtract memavailable from memtotal to get what top htop tell you

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Linux  In Linux  this information is available in the  proc file system   I m not a big fan of the text file format used  as each Linux distribution seems to customize at least one important file   A quick look as the source to  ps  reveals the mess   But here is where to find the information you seek    proc meminfo contains the majority of the system-wide information you seek   Here it looks like on my system  I think you are interested in MemTotal  MemFree  SwapTotal  and SwapFree   Anderson cxc   more  proc meminfo MemTotal       4083948 kB MemFree        2198520 kB Buffers          82080 kB Cached         1141460 kB SwapCached           0 kB Active         1137960 kB Inactive        608588 kB HighTotal      3276672 kB HighFree       1607744 kB LowTotal        807276 kB LowFree         590776 kB SwapTotal      2096440 kB SwapFree       2096440 kB Dirty               32 kB Writeback            0 kB AnonPages       523252 kB Mapped           93560 kB Slab             52880 kB SReclaimable     24652 kB SUnreclaim       28228 kB PageTables        2284 kB NFS Unstable         0 kB Bounce               0 kB CommitLimit    4138412 kB Committed AS   1845072 kB VmallocTotal    118776 kB VmallocUsed       3964 kB VmallocChunk    112860 kB HugePages Total      0 HugePages Free       0 HugePages Rsvd       0 Hugepagesize      2048 kB   For CPU utilization  you have to do a little work   Linux makes available overall CPU utilization since system start  this probably isn t what you are interested in   If you want to know what the CPU utilization was for the last second  or 10 seconds  then you need to query the information and calculate it yourself   The information is available in  proc stat  which is documented pretty well at http   www linuxhowtos org System procstat htm  here is what it looks like on my 4-core box   Anderson cxc    more  proc stat cpu  2329889 0 2364567 1063530460 9034 9463 96111 0 cpu0 572526 0 636532 265864398 2928 1621 6899 0 cpu1 590441 0 531079 265949732 4763 351 8522 0 cpu2 562983 0 645163 265796890 682 7490 71650 0 cpu3 603938 0 551790 265919440 660 0 9040 0 intr 37124247 ctxt 50795173133 btime 1218807985 processes 116889 procs running 1 procs blocked 0   First  you need to determine how many CPUs  or processors  or processing cores  are available in the system   To do this  count the number of  cpuN  entries  where N starts at 0 and increments   Don t count the  cpu  line  which is a combination of the cpuN lines   In my example  you can see cpu0 through cpu3  for a total of 4 processors   From now on  you can ignore cpu0  cpu3  and focus only on the  cpu  line   Next  you need to know that the fourth number in these lines is a measure of idle time  and thus the fourth number on the  cpu  line is the total idle time for all processors since boot time   This time is measured in Linux  jiffies   which are 1 100 of a second each    But you don t care about the total idle time  you care about the idle time in a given period  e g   the last second   Do calculate that  you need to read this file twice  1 second apart Then you can do a diff of the fourth value of the line   For example  if you take a sample and get   cpu  2330047 0 2365006 1063853632 9035 9463 96114 0   Then one second later you get this sample   cpu  2330047 0 2365007 1063854028 9035 9463 96114 0   Subtract the two numbers  and you get a diff of 396  which means that your CPU had been idle for 3 96 seconds out of the last 1 00 second   The trick  of course  is that you need to divide by the number of processors   3 96   4   0 99  and there is your idle percentage  99  idle  and 1  busy   In my code  I have a ring buffer of 360 entries  and I read this file every second   That lets me quickly calculate the CPU utilization for 1 second  10 seconds  etc   all the way up to 1 hour   For the process-specific information  you have to look in  proc pid  if you don t care abut your pid  you can look in  proc self   CPU used by your process is available in  proc self stat   This is an odd-looking file consisting of a single line  for example   19340  whatever  S 19115 19115 3084 34816 19115 4202752 118200 607 0 0 770 384 2  7 20 0 77 0 266764385 692477952 105074 4294967295 134512640 146462952 321468364 8 3214683328 4294960144 0 2147221247 268439552 1276 4294967295 0 0 17 0 0 0 0   The important data here are the 13th and 14th tokens  0 and 770 here    The 13th token is the number of jiffies that the process has executed in user mode  and the 14th is the number of jiffies that the process has executed in kernel mode   Add the two together  and you have its total CPU utilization   Again  you will have to sample this file periodically  and calculate the diff  in order to determine the process s CPU usage over time     Edit   remember that when you calculate your process s CPU utilization  you have to take into account 1  the number of threads in your process  and 2  the number of processors in the system   For example  if your single-threaded process is using only 25  of the CPU  that could be good or bad   Good on a single-processor system  but bad on a 4-processor system  this means that your process is running constantly  and using 100  of the CPU cycles available to it   For the process-specific memory information  you ahve to look at  proc self status  which looks like this   Name    whatever State   S  sleeping  Tgid    19340 Pid     19340 PPid    19115 TracerPid       0 Uid     0       0       0       0 Gid     0       0       0       0 FDSize  256 Groups  0 1 2 3 4 6 10 11 20 26 27 VmPeak    676252 kB VmSize    651352 kB VmLck          0 kB VmHWM     420300 kB VmRSS     420296 kB VmData    581028 kB VmStk        112 kB VmExe      11672 kB VmLib      76608 kB VmPTE       1244 kB Threads         77 SigQ    0 36864 SigPnd  0000000000000000 ShdPnd  0000000000000000 SigBlk  fffffffe7ffbfeff SigIgn  0000000010001000 SigCgt  20000001800004fc CapInh  0000000000000000 CapPrm  00000000ffffffff CapEff  00000000fffffeff Cpus allowed    0f Mems allowed    1 voluntary ctxt switches         6518 nonvoluntary ctxt switches      6598   The entries that start with  Vm  are the interesting ones    VmPeak is the maximum virtual memory space used by the process  in kB  1024 bytes   VmSize is the current virtual memory space used by the process  in kB   In my example  it s pretty large   651 352 kB  or about 636 megabytes  VmRss is the amount of memory that have been mapped into the process  address space  or its resident set size   This is substantially smaller  420 296 kB  or about 410 megabytes    The difference   my program has mapped 636 MB via mmap    but has only accessed 410 MB of it  and thus only 410 MB of pages have been assigned to it    The only item I m not sure about is Swapspace currently used by my process   I don t know if this is available

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Linux  A portable way of reading memory and load numbers is the sysinfo call  Usage      include  lt sys sysinfo h gt      int sysinfo struct sysinfo  info     DESCRIPTION     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

[c++] How to determine CPU and memory consumption from inside a process?

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