System Calls vs. Procedure Calls:

How much more expensive is a system call than a procedure call? Write a simple test program to compare the cost of a simple procedure call to a simple system call ("getpid()" is a good candidate on UNIX; see the man page.) (Note: be careful to prevent the optimizing compiler from "optimizing out" your procedure calls. Do not compile with optimization on.)

• Run your experiment on two different hardware architectures and report the results.
• Explain the difference (if any) between the time required by your simple procedure call and simple system call by discussing what work each call must do (be specific). [Note: Do not provide the source code for your program, just the results].

Hint: You should use system calls such as gethrtime() or gettimeofday() for time measurements. Design your code such that the measurement overhead is negligible. Also, be aware that timer values in some systems have limited resolution (e.g., millisecond resolution).

You will be presenting your results in class. To have some confidence in your results it might be good to have several implementations.

This assignment from Professor Dahlin