21. A given program runs in 8 minutes on one Intel Pentium 4 processor. How long

Question

21. A given program runs in 8 minutes on one Intel Pentium 4 processor. How long would it take to execute the same program on a multiprocessor system with 4 (four) identical Intel Pentium 4 processors? Explain your answer (Assume that there are no other user processes in the system). 22. Briefly explain the function of the medium-term scheduler. How can it improve the system performance? Explain. 23. The Android operating system defines a hierarchy of importance among the processes. What is the motivation for defining such a hierarchy? How would the system performance be affected if such a hierarchy was not defined?

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Q21)

Answer)
As we know here, that the program executes in 8 minutes on one Intel Pentium 4 processor. We need to calculate the time to execute the same program, on multiprocessor system using 4 Intel Pentium 4 processors.

Using Amdahl's Law,

1/((1-P)+(P/N)

Let us assume that the entire program can be made parallel.
Thus P is the potion of the program that can be made parallel = 1. Thus 1-P = 0
Also, N, the number of processors = 4 here.

1/((1-P)+(P/N)
= 1 / (0 + 1/4)
= 1 / .25
= 4

Thus the speedup will be 4 times.

Thus the time taken to execute the same program, on multiprocessor system using 4 Intel Pentium 4 processors will be =
8/4 = 2 minutes.

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