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Analysing Performance of Real-Time Systems and their Quality of Services

SYSC 4805/4806 Presentation Alim Mehmet Baytekin Colin MacDougall Joshua Delrio. Analysing Performance of Real-Time Systems and their Quality of Services. What are Real-Time Systems?. Real-time systems are subject to “real-time constraints” Time Critical Criticality of response time

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Analysing Performance of Real-Time Systems and their Quality of Services

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  1. SYSC 4805/4806 Presentation Alim Mehmet Baytekin Colin MacDougall Joshua Delrio Analysing Performance of Real-Time Systemsand their Quality of Services

  2. What are Real-Time Systems? • Real-time systems are subject to “real-time constraints” • Time Critical • Criticality of response time • How important is that deadline? • 'Soft' and 'Hard' real-time systems • Examples of real-time systems: • Elevator Systems • Car Control Systems • Radio Broadcasts

  3. Soft Real-Time Systems • Results degrade in usefulness past deadline • Missed deadlines do not result in system failure • More adaptive – error tolerance, recovery • Example: • Live bus schedule system – missed deadline of response from a bus might result in incorrect arrival estimates • Late responses from buses reduce the usefulness of the response; a sub-optimal route might be suggested in err

  4. Hard Real-Time Systems • Results are useless past deadline • Missed deadlines result in system failure • Rigid in implementation – not error tolerant • Example: • Pacemaker – Critical for system to respond within deadline • Missed deadlines might result in dead lines

  5. Testing: Functionality & Performance • Functionality testing: does system work as intended? • Metrics not generally analysed, but still vital • Performance testing: how well does system work? • Metrics are analysed and compared; optimization • Does the system meet the performance criteria? • Does the system outperform competitors? • What is the system's bottleneck? [1]

  6. Metrics – Measuring Performance • Metrics are units of measure • Four main groups of software metrics [2] • Schedule: speed, timing • Size/Complexity: memory usage, scalability • Cost: will your project cost an arm and a leg? • Quality: packet loss, sustained throughput

  7. Soft Real-Time – Case Scenario • Search Engine System • Identify focus: search speed; gain edge over competitors • Main Criteria: speed • Combining metrics to address focus: • Speed comparison graphs • Use metrics to identify bottlenecks • potential server utilization maxed – slowing down searches

  8. Hard Real-Time – Case Scenario • PCRF – Policy Charging Rules Function • Phone operators use this to charge customers • Identify Focus: reliable 100% uptime • Main criteria: scalability, redundancy • Combining metrics to address focus: • Scalability versus speed • Amount of redundancy versus speed • Use metrics to identify bottlenecks.

  9. Figure 1 – PCRF Metric Example[3]

  10. What is Quality of Service? (QoS) • Provide variable priorities to different parts of the system to guarantee performance • Quality of Service sets minimum quality requirements for different metrics (bit rate, jitter, errors) • 4G Telecom QoS Examples: • Voice • Data • Texting • Video • Etc.

  11. QoS and Performance • Measuring performance of QoS requires the following: • An understanding of the QoS function • A general idea of which metrics have higher priority • Balance metrics to adhere to minimum QoS guidelines • PCRF – Conversational VoIP, Conversational Video, Non-Conversational Video, Real Time Gaming, Texting, Voice/Video/Interactive Games, Video/TCP Apps (email)

  12. Figure 2 – LTE QoS-based Data Flow Specifications[4]

  13. Summary • Four main groups of metrics: • Schedule • Size/Complexity • Cost • Quality • These metrics are used to: • Meet criteria (QoS) • Outperform competitors • Identify and address bottlenecks • Qualities of Service • Minimum performance criteria • Balance metrics to adhere to specifications

  14. References • [1] http://en.wikipedia.org/wiki/Software_performance_testing, Software Performance Testing – Setting performance goals, Retrieved March 4th. • [2] Http://en.wikipedia.org/wiki/Software_metric, Software Metric – Limitations, Retrieved March 4th. • [3] http://developingsolutions.com/datasheets/PcrfTesting.pdf, PCRF Test Methodology, Retrieved March 4th. • [4] http://wirelessweek.com/articles/2010/10/part-3-interoperability-and-qos-lte-networks, Part 3: Interoperability and QoS in LTE Networks, Retrieved March 4th.

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