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Get CPU Usage with GetSystemTimes

, 20 Dec 2004 Public Domain
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Get CPU usage with GetSystemTimes.
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      From a very long time, a lot of people wanted to get the CPU usage from the computer.

      You've a lot of way to do this like calling registry like key or PerfCounter. But TaskManager doesn't call any of these ... If you're looking from the import table of TaskManager you can find:

        Import Adress Table: 0x00001414
        Import Name Table: 0x00013C2C
            0x7C90E213 260 NtQueryVirtualMemory
            0x7C90DDF9 209 NtOpenThread
            0x7C90D586 103 NtClose
            0x7C90E1AA 255 NtQuerySystemInformation

      So there is no other solution to have this information to dig into undocumented NtQuerySystemInformation. With this nice warning at the beginning of the article:[ NtQuerySystemInformation is available for use in Windows 2000 and Windows XP. It may be altered or unavailable in subsequent versions. Applications should use the alternate functions listed in this topic.]

      No other solution?

      Well GetSystemTimes is a good function if you have the Requirements

      Client         Requires Windows XP SP1. 
      Server         Requires Windows Server 2003. 
      Header         Declared in Winbase.h; include Windows.h.
      Library        Link to Kernel32.lib.
      DLL            Requires Kernel32.dll. 

      How to use it?

      Call this :

      FILETIME idleTime;
      FILETIME kernelTime;
      FILETIME userTime;
      BOOL res = GetSystemTimes( &idleTime, &kernelTime, &userTime );

      and voilà you have almost what you need.

      Now you have to poll this function and make a little calculus.

      usr = userTime - last_userTime;
      ker = kernelTime - last_kernelTime;
      idl = idleTime - last_idleTime;

      System time is:

      sys = kerl + usr

      idleTime is the rest because "System Idle" process is taking 100 % of CPU.

      So CPU is :

      cpu = int( (sys - idl) *100 / sys );


      It was a very long wait before Microsoft gave us this function. Now it's done but there is still one problem. For multiple processor system, you don't have the right information.

      In the sample you can find the use of GetSystemTimes and GetProcessTimes and a little class to do everything.

      class CPU
        CPU( void );
        ~CPU( void );
        // return :
        // % of cpu usage for this process 
        // % cpu systemUsage 
        // uptime for this process
        int GetUsage( int* pSystemUsage, TKTime* pUpTime );
    • License

      This article, along with any associated source code and files, is licensed under A Public Domain dedication


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      Comments and Discussions

      GeneralRe: The way it's supposed to be... PinmemberMember 442588919-Mar-10 11:39 
      GeneralRe: The way it's supposed to be... PinmemberVitaly Tomilov19-Mar-10 12:09 
      GeneralRe: The way it's supposed to be... Pinmemberdxj1983102921-Jul-10 19:45 
      GeneralGood coding practices PinmemberAbbas Ibn Fernas24-Mar-10 0:46 
      GeneralRe: The way it's supposed to be... PinmemberVider20-Dec-11 2:29 
      GeneralRe: The way it's supposed to be... PinmemberDan Bloomquist29-May-13 17:56 
      GeneralMessy PinmemberVitaly Tomilov2-Sep-08 6:44 
      GeneralNice! PinmemberVitaly Tomilov23-Aug-08 8:15 
      This article got me started to implement CPU usage the right way.
      I'm running it on Vista, and seeing always 0 for the Process, but correct values for the CPU usage.
      Did you do any further research in this direction after the article?
      This is still a problem even today how to get CPU usage properly.
      Just studying your code, and the first thing i noticed: you call LoadLibrary + FreeLibrary for kernel32.dll. You shouldn't do that, because kernel32.dll is always residing withing any process, so you must call GetModuleHandle instead, and never call FreeLibrary, that is the right way.
      If you ever made any improvement to this example, i would be very nice to see here Wink | ;)
      I appreciate if you come back to me on this, as i'm working on an article with similar subject, about CPU information in general.
      Professional System Library on

      GeneralRe: Nice! Pinmemberejor23-Aug-08 9:27 
      GeneralRe: Nice! PinmemberVitaly Tomilov23-Aug-08 9:38 
      GeneralDoesn't compile... PinmemberPaul Conrad9-Dec-07 13:31 
      GeneralCurrent Process % cpu utilisation Pinmemberkintz6-Jul-06 5:10 
      AnswerRe: Current Process % cpu utilisation Pinmemberejor29-Oct-06 11:06 
      QuestionCode bug? Pinmemberkintz6-Jul-06 0:24 
      AnswerRe: Code bug? Pinmemberejor6-Jul-06 2:31 
      Generalmultiple processor Pinmemberhxtking6-Apr-06 11:45 
      GeneralRe: multiple processor Pinmemberejor6-Apr-06 12:02 
      Questionhow about cygwin ? Pinmemberpersonalcomputer25-Feb-06 0:23 
      AnswerRe: how about cygwin ? Pinmemberejor26-Feb-06 0:29 
      QuestionWhy is "System Idle" process 100% of CPU? Pinmemberdmtwpi2120-Jan-06 10:59 
      AnswerRe: Why is "System Idle" process 100% of CPU? Pinmemberejor20-Jan-06 11:04 
      GeneralWindows CE support Pinmemberronannaughton25-Oct-05 15:18 
      GeneralRe: Windows CE support PinmemberShanmuga Sundar.V8-May-08 4:57 
      Generalremote computers PinmemberPeterK200325-Aug-05 10:11 
      GeneralRe: remote computers Pinmemberejor25-Aug-05 10:21 

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