1. Software Architecture in Practice
Theoretical Exercise in Performance Engineering

2. Exercise 1a: Response Time Calculation
Web Browser
What is the end-user response time?
Assume:
Network latency (transmission time overhead) is 500ms
User transaction arrival rate is fixed and exponentially distributed across the user community
Ignore processing time of browser
Hints:
Network: Use the utilization law
Server: Use graphs of service time under increasing load for server response time OR calculate using formula for response time
Web Browser
(per user)
150 users
12 txn per min
Amount of data sent over network
1 Mbps
per user
20 KB
Internet
100 KB
Web Server
0.03 s service time
uni-processor system

3. Exercise 1b: Amdahl’s Law
Suppose that we are considering an enhancement to the processor of a server system used for Web serving.
The new CPU is 10 times faster on computation in the Web serving application than the original processor.
Assuming that the original CPU is busy with computation 40% of the time and is waiting for I/O 60% of the time, what is the overall speedup gained by incorporating the enhancement?

4. Group work