Question

Assume you are a system administrator of the company and found two usage peaks between 12:00AM to
3:00PM and between 8:00PM to 11:00PM. The CEO asked you to design a system where during these
peak hours there will be three levels of users as follows: the users in level 1 can enjoy better response time
than the users in level 2, who in turn will enjoy better response time than the users in level 3. Your system
can allow all users still get some progress, but with the indicated preference in place.
(1). If we use a fixed priority scheme with preemption and set the levels as the three priorities, does this
scheme can work? Defend your answers.
(2). Will a multi-feedback queue work? Defend your answers.

Answer 1

1.The answer for first question is No.It doesn't work.A fixed priority scheme can cause starvation. Also the required solution should enable all users to make progress. Fixed priority does not guarantee progress for processes with low priorities.

2. The second answer is also No.It doesn't work. The multi-feedback queuing system will cause processes in level 1 to get less time on the CPU if they stay in the system for very long.

So, even though a level-1 process may start at the highest level in the feedback
queue, its priority will degrade over time. So this solution does not satisfy the requirements.