Download W8-3 Exercise 1

Software Architecture in Practice
Theoretical Exercise in Performance
Engineering
Exercise 1a: Response Time
Calculation
Web Browser
Web Browser
(per user)
150 users
12 txn per min
•
•
– 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
100 KB
Internet
20 KB
Amount of
data sent
over network
1 Mbps
per user
Web Server
0.03 s service time
uni-processor
system
What is the end-user response time?
Assume:
•
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
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?
Group work