C++ GetProcessTimes() does not change value over time - c++

Question

I'm writing a C++ function for get CPU usage of specific process in Windows.
Many reference (like this) suggest using function GetProcessTimes for implementation.
However, I tried with a sample program but the value of KernelTime and UserTime is not changed over times.Below is my code:
#include <iostream>
#include <Windows.h>
int main()
{
int processID = 14532;
HANDLE processHandle = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, processID);
if (processHandle == NULL) {
return -1;
}
FILETIME ftProcCreation, ftProcExit, ftProcKernel, ftProcUser;
for (int i = 0; i < 10; i++) {
if (!GetProcessTimes(GetCurrentProcess(), &ftProcCreation,
&ftProcExit, &ftProcKernel, &ftProcUser)) {
return -1;
}
LARGE_INTEGER lKernel, lUser;
lKernel.LowPart = ftProcKernel.dwLowDateTime;
lKernel.HighPart = ftProcKernel.dwHighDateTime;
lUser.LowPart = ftProcUser.dwLowDateTime;
lUser.HighPart = ftProcUser.dwHighDateTime;
printf("%lld : %lld\n", lKernel.QuadPart, lUser.QuadPart);
Sleep(250);
}
}
The process that I inspect is a running Virtualbox process that always take about 20% of CPU.
However, when I run the sample code, the result is as below:
0 : 0
0 : 0
0 : 0
0 : 0
0 : 0
0 : 0
0 : 0
0 : 0
0 : 0
0 : 0
Sometimes, it might give following result:
312500 : 0
312500 : 0
312500 : 0
312500 : 0
312500 : 0
312500 : 0
312500 : 0
312500 : 0
312500 : 0
312500 : 0
Again, it might give following result:
156250 : 0
156250 : 0
156250 : 0
156250 : 0
156250 : 0
156250 : 0
156250 : 0
156250 : 0
156250 : 0
156250 : 0
Or might be:
0 : 156250
0 : 156250
0 : 156250
0 : 156250
0 : 156250
0 : 156250
0 : 156250
0 : 156250
0 : 156250
0 : 156250
And so on, but the value of "0:0" is more frequency.
Is there any wrong with my code, so that it cannot get Kernel/Idle time of the process? And why the value does not change over time?
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Answer 1

You're querying the time of the current process (GetCurrentProcess()), not the target process (processHandle). Since GetProcessTimes() returns the CPU time consumed by the process, but your process isn't consuming much time as it is mostly sleeping, the result changes very slowly.
So, pass processHandle instead of GetCurrentProcess() to GetProcessTimes().