http://blog.csdn.net/ljinddlj/article/details/5343209
struct timeval t_start,t_end;     long cost_time = 0;   //get start time gettimeofday(&t_start, NULL); printf("Start time: %ld us", t_start.tv_usec);   //some operation …   //get end time gettimeofday(&t_end, NULL); printf("End time: %ld us", t_end.tv_usec);   //calculate time slot cost_time = t_end.tv_usec - t_start.tv_usec; printf("Cost time: %ld us", cost_time); …   输出： Start time: 438061 us End time: 459867 us Cost time: 21806 us