An example of using SHARPE to evaluate computer system perofrmance.
Based on the model provided in: Marsan, M. A., & Gerla, M. (1982). Markov models for multiple bus multiprocessor systems. IEEE Transactions on Computers, (3), 239-248.
In this example we consider a system with 4 processors, 4 common memories and 2 buses with the following considerations:
- Processors execute on there own private cache and then perform some operations on a common memory.
- The rate of requesting common memories is exponentially distrbuted and defined as Lambda.
- The processor selects a common memory randomly with equal probaility 1/4.
- The rate of releasing the common memory by a processor is exponentially distrbuted and defined as Mu.
- When a memory or bus is not free, the processor will wait.
- The system performance is evaluated as the count of processors executing or accessing the common memory.
The system is modeled as a markov chain, the system is in a state "A-B-C" where:
- A: The count of processors accessing common memory.
- B: The count of processors waiting for memories.
- C: The count of processors waiting for a free bus.
We evaluate the performance of the system by assigning a reward for each state that corresponds to the number of active processors. We then calculate the "Expected Steady State Reward" for the system.
We consider Rho = Mu / Lambda ranging from 0 to 1.
