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Performance Engineering Methodology

Performance Engineering Methodology. Chapter 4. Performance Engineering. Performance engineering analyzes the expected performance characteristics of a system during the different phases of its lifecycle. Performance engineering

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Performance Engineering Methodology

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  1. Performance Engineering Methodology Chapter 4

  2. Performance Engineering • Performance engineering analyzes the expected performance characteristics of a system during the different phases of its lifecycle. • Performance engineering • 1) develops practical strategies that help predict the level of performance a system can achieve and • 2) provides recommendations to realize the optimal performance level.

  3. Typical PE Questions • Can the insurance claim system meet its performance requirements of sub-second response time when a natural disaster occurs (e.g., a hurricane). Response Time • Is the infrastructure of a government agency scalable and can it cope with the computing demands of the new required online security mechanisms? Scalability • Is the reservation system for cruise lines able to respond to anticipated peak of customer inquiries after a TV ad campaign? Reliability

  4. PE Larger Questions • How can one plan, design, develop, deploy, and operate IT services that meet ever increasing demands for performance, availability, reliability, and security? • Is a given IT system properly designed and sized for a given load condition?

  5. PE Activities • Understand the key factors that affect a system’s performance. • Measure the system and understand its workload. • Develop and validate a workload model that captures the key characteristics of the actual workload. • Develop and validate an analytic model that accurately predicts the system’s performance. • Use the models to predict and optimize the system’s performance.

  6. Modeling Process

  7. Motivating Example: a Call Center

  8. Call Center • Goals: • Foster better relationships with customers, creating customer loyalty and ensuring quality service. • Improve efficiency and service performance. • Identify and explore new sales opportunities. • Main Functions: • Order status inquiry • Shipment tracking • Problem resolution status inquiry • Requirements: sub-second response time and 24x7 operation.

  9. QoS Questions • Is the system design able to meet the subsecond response time for all functions? Response Time • What will be the impact of doubling the number of system representatives in the next year? Scalability • Can acceptable performance levels be maintained after integrating the system with the mainframe-based inventory application? Scalability • Is the system capacity adequate to handle up to 1,000 calls in the busiest hour and yet preserve the subsecond response time goal? • How do failures in the database server affect the 24x7 availability goal? • What is the impact of starting to offer Web-based self-service to customers?

  10. At the Requirements AnalysisPhase • Workload definition: • Call center’s view: Arrival rate of phone calls • IT system’s view: Functions received from the representatives. • DB server view: SQL requests from the application server. • LAN view: packet size distribution and interpacketarrival time.

  11. At the System Design Phase • What should the system throughput be to meet sub-second response times? • 200 customer service representatives and 80% are working during the peak hour. • Average think time of 30 sec. Model of the call center system

  12. Call Center Model • Z: average think time, 30sec • N: number of active representatives in the system, 200X80% = 160 • X0: system throughput • R: average response time < 1sec • Using the interactive response time law:

  13. At the System Development Phase • What should be the capacity of the DB server so that the performance goals are met? • Each submitted functions requires 2.2 SQL calls on average. • From the Forced Flow Law:

  14. At the Operation Phase • Assume DB server is a problem. Response times exceed sub-second goal. • Measurements during peak hour: • 57600 queries/hour • Each query needs 50 msec of CPU, performs 4 I/Oson disk 1 and 2 I/Os on disk 2. Each I/O takes 8 msec on average. • X0 = 57600 / 3600 = 16 queries/sec • Service demands: • Dcpu= 0.05 sec; • Ddisk1 = 4 x 0.008 = 0.032 sec; • Ddisk2 = 2 x 0.008 = 0.016 sec.

  15. At the Operation Phase (cont’d)

  16. At the Operation Phase (cont’d) • The residence times at the CPU and disks for open QN model • Response time of the DB server: • RDB =

  17. At the Evolution Phase • The company is considering to develop Web applications to allow customers access to the information they need without assistance from a customer representative. Web self-services reduce transaction costs and enhance the customer experience. • Security requirements mandate that new applications be developed for Web access (authentication, auditing, DB access control mechanisms).

  18. At the Evolution Phase • Local queries and web queries:

  19. Results for Evolution Scenario

  20. Results for Evolution Scenario

  21. Performance Engineering Methodogy

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