Assuming that you are the administrator of an interactive computer system. The computer system consists of a multi-core CPU and a disk. During an observation time of 1800 seconds, you obtained the following measurements from the system:
Average busy time per core 1575
Disk busy time 1124 s
Number of requests completed by the computer system 57
This computer system is used by 16 interactive users and the thinking time per interactive user is 45 seconds.
You consider the current throughput of the system is too low. You are considering a proposal to upgrade the current CPU, which has 4 cores, to a new CPU with 6 cores and the same processing speed per core as that of the current CPU.
For this question, you can assume that the workload remains the same before and after the upgrade. You can also assume that the workload is almost evenly distributed among the cores at the moment and the workload can still be evenly distributed among the cores after the upgrade. As the system administrator, you know that when the workload uses the CPU, it uses only one core at a time, i.e., the workload does not use multiple cores concurrently.
Answer the following questions.
(a) Determine the current average service demand of a core.
(b) What will the average service demand per core be if the proposed CPU upgrade is carried out? Hint: The service demand of a core depends on two factors: the number of visits to the core and the service time needed per visit to the core. For the set up of this question, one of these two factors remains the same after the upgrade, while the other factor will change.
(c) What will the throughput bound of the computer system be if the proposed CPU upgrade is carried out?