Timing in Linux -- gettimeofday Function

Use C language for timing
In user space, you can use the C language function gettimeofday to get the time. The call format is:

# Include <sys/time. h>
Int gettimeofday (struct timeval * TV, struct timezone * tz );
Int settimeofday (const struct timeval * TV, const struct timezone * tz );
The timeval structure is defined:
Strut timeval {long TV _sec;/* seconds */long TV _usec;/* microseconds */};

It can be seen that with this method, the precision can reach microseconds, that is, 10-6 seconds. During timing, we need to call gettimeofday twice before and after, and then calculate the difference value in the middle:

Gettimeofday (& START, null );
Foo ();
Gettimeofday (& End, null );
Timeuse = 1000000 * (end. TV _sec-start. TV _sec) + end. TV _usec-start. TV _usec;
Timeuse/= 1000000;