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Perf. Eval., Homework 4 (due 10.4.2002)

1. Prove that formula 7-1 in Lecture 7 is correct:
   
   
2. Give examples on when normalization constant G could overflow/underflow. How can you avoid this problem?
   
   
3. Assume that your system has a dual-processor CPU. How does that change the ABA and BJB bounds computations?

    

4. [2 htp] A computer system has one CPU and  two disks (disk1 and disk2). System was monitored for one hour and utilization of CPU and disk1 were found to be 32% and 60%, respectively. Each transaction makes 5 I/O requests to disk1, and 8 I/O requests to disk2. Average service time to disk1 is 30 msec, and to disk2 25 msec. [Men 94, p. 173].
   1. Find the system throughput.
   2. Find disk2 utilization.
   3. Find average service demands at each device.
   4. With MVA, find system throughput, response time and average queue lengths at each device with mpl=0, 1, 2, 3, and 4.
   5. What was the average mpl during the original 1 hour measurement interval?

   For MVA solution you should use PMVA[Brumfield 81].

   An executable copy of PMVA is available as /home/fs/kerola/bin/pmva and it can be executed from most deparmental Linux machines (E.g., melkki, melkinkari). For example, to run model /home/fs/kerola/pmva/ex1.pmva in PMVA you need to login to such machine and execute command
   
               /home/fs/kerola/bin/pmva </home/fs/kerola/pmva/ex1.pmva

   A copy of the PMVA manual is available in the course folder in A412.

    

5. [2 htp] Use PMVA to solve the following model exactly.
                  
   Aggregate I/O subsystem (devices disk1 and disk2) to one load dependent device and solve the aggregate model with PMVA. Compare results to those of exact model. What is good/bad in your aggregate solution?
   What does it mean that aggregate model solution is "good"?
   Repeat the experiment with just 4 users. Is aggregate solution with this population level better or worse than with population 20? Why?