Test multiple iterations of fsync-ing small amounts of data

/*
 Test multiple iterations of fsync-ing small amounts of data

 gcc [filename] -lrt
*/

#include <unistd.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <stdio.h>

double timespecdif(const struct timespec *start,const struct timespec *end) {
 time_t tdif=difftime(end->tv_sec,start->tv_sec);
 long ndif=end->tv_nsec-start->tv_nsec;
 if (ndif<0) {tdif-=1; ndif+=1000000000;}
 return (double)tdif+ndif*0.000000001;
}

int main(int argc,char* argv[]) {
 double o;
 int i;
 int iterations=16;
 struct timespec start,end,prev;
 int file=open("test",O_WRONLY);
 if (argc>1) {
  int q=atoi(argv[1]);
  if (q) iterations=q;
 }
 printf("Doing %d iterations.\n",iterations);
 clock_gettime(CLOCK_MONOTONIC,&end);
 memcpy(&start,&end,sizeof(start));
 memcpy(&prev,&end,sizeof(start));
 for (i=0; i<iterations; i++) {
  write(file,"abcd",4);
  fsync(file);
  clock_gettime(CLOCK_MONOTONIC,&end);
  o=timespecdif(&prev,&end);
  memcpy(&prev,&end,sizeof(end));
  printf("%.03f\n",o);
  fflush(stdout);
 }
 clock_gettime(CLOCK_MONOTONIC,&end);
 o=timespecdif(&start,&end);
 printf("Total time taken %.03f seconds.\n",o);
 close(file);
}