BBC BASIC Programmers' Reference

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Finding the CPU usage

by Richard Russell, October 2011

The code listed below reports, once per second, the current total CPU usage:

FLOAT 64

      DIM IdleTime{l%,h%}, KernelTime{l%,h%}, UserTime{l%,h%}

      idletime = 0
      kerneltime = 0
      usertime = 0
      REPEAT
        WAIT 100
        SYS "GetSystemTimes", IdleTime{}, KernelTime{}, UserTime{}

        oldidletime = idletime
        oldkerneltime = kerneltime
        oldusertime = usertime
        idletime = IdleTime.h% * 2^32 + (IdleTime.l% >>> 1)*2
        kerneltime = KernelTime.h% * 2^32 + (KernelTime.l% >>> 1)*2
        usertime = UserTime.h% * 2^32 + (UserTime.l% >>> 1)*2

        idledelta = idletime-oldidletime
        kerneldelta = kerneltime-oldkerneltime
        userdelta = usertime-oldusertime

        cpuusage = (userdelta+kerneldelta-idledelta)/(userdelta+kerneldelta)
        PRINT "CPU usage = ";INT(100*cpuusage+0.5) "%"

      UNTIL FALSE