measuring speed of a system call

Question

I am trying to optimize our gettimeofday() system call on Redhat Linux. By their documentation it can be speed by running the call in the user land using virtual dynamic shared object (VDSO). I was curious how can I mesure the speed of the call in the first place? I would like to make the change and then compare it against my previous results

Answer 1

Pseudocode:

1. call gettimeofday() and save result in a
2. call gettimeofday() a million times
3. call gettimeofday() and save result in b
4. Calculate (b-a)/1,000,000

Rationale: The two bounding calls to gettimeofday() should not make much of an impact on the loop. It may feel strange to call the function that you want to time but that's OK.