CS372H Spring 2011 Homework 1

Problem 1

Problem 2

        * Compiler
        * Linker
        * Loader
        * Boot module or boot ROM

Problem 3

        1. What is the effect of having such a large number of registers on the operating system?
        2. What additional hardware features you would recommend added to the design above.
        3. What happens if the hardware designer also wants to add a 16-station pipeline into the CPU. How would that affect the context
            switching overhead?

Problem 4

main(int argc, char ** argv)
{
int child = fork();
int c = 5;

if(child == 0)
{

c += 5;
}
else
{
child = fork();
c += 10;
if(child)
c += 5;
}
}
 

Problem 5

main(int argc, char ** argv)
{
forkthem(5)
}
void forkthem(int n)
{
if(n > 0)
{
fork();
forkthem(n-1);
}
}

Problem 6

Program 1:
main()
{
    val = 5;
    if(fork())
        wait(&val);
    val++;
    printf("%d\n", val);
    return val;
}

Program 2:
main()
{
    val = 5;
    if(fork())
        wait(&val);
    else
        exit(val);
    val++;
    printf("%d\n", val);
    return val;
}
 

Problem 7

A typical hardware architecture provides an instruction called return from interrupt, and abbreviated by something like iret. This instruction switches the mode of operation from supervisor mode to user mode. This instruction is usually only available while the machine is running in supervisor mode.

    1. Explain where in the operating system this instruction would be used.
    2. What happens if an application program executes this instruction?

Problem 8

• 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).

Problem 9 (this one is tough)