Dear All,
I was experimenting with the timing and timing accuracy on BBB. and I came
across a very *interesting* yet strange thing!
Just running clock_gettime()twice and measuring the time difference, gives
you horrendous timing. Here is my simple C code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
int main()
{
struct timeval startTime, stopTime;
clock_gettime(CLOCK_REALTIME, &sT);
printf("\n%ld.%09ld\n" ,sT.tv_sec,sT.tv_nsec);
clock_gettime(CLOCK_REALTIME, &eT);
printf("\n%ld.%09ld %ld uSec\n" , eT.tv_sec, eT.tv_nsec, ((eT.tv_sec -
sT.tv_sec)*1000000 + (eT.tv_nsec-sT.tv_nsec)/1000));
return 0;
}
Just two gettime are causing *2894 to 3200 micro sec* (uSec) time
difference, how is such huge amount possible!??
Can someone throw some light on this? and can it be improved or fixed?
I have tried the following to investigate.
1) Running same code on my i7
it gives 80uS to ~300 uS delay.
2) Trying TimeVal and GetTimeOfDay -- gives worse result!
3) Running NTP:
No impact.
Thank you, and hope you find it interesting as well :)
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