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Computer Performance

Computer Performance. What is it? How do we measure it? How do we compare two performance measures?. Airplane Performance. Which plane has the best performance?. Defining Computer Performance. Various possibilities Response (a.k.a. execution) time Throughput.

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Computer Performance

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  1. Computer Performance • What is it? • How do we measure it? • How do we compare two performance measures? Ch.2 - The Role of Performance

  2. Airplane Performance • Which plane has the best performance? Ch.2 - The Role of Performance

  3. Defining Computer Performance • Various possibilities • Response (a.k.a. execution) time • Throughput Ch.2 - The Role of Performance

  4. Defining Computer Performance • Various possibilities • Response (a.k.a. execution) time • Throughput Ch.2 - The Role of Performance

  5. Relative Performance Ch.2 - The Role of Performance

  6. Measuring Performance • Elapsed time (a.k.a. wall-clock time, response time) • CPU execution time • User CPU time • System CPU time • Convention • System performance: elapsed time on unloaded computer • CPU performance: user CPU time Ch.2 - The Role of Performance

  7. Another Performance MetricClock cycles • How many cycles of the processors internal clock does it take for the program to execute? Ch.2 - The Role of Performance

  8. Execution Time vs. Cycles Ch.2 - The Role of Performance

  9. Instruction Times • Processor instructions take some number of (clock) cycles to complete • Duration might vary based on data • Clock Cycles per Instruction (CPI):average number of clock cycles per instruction for a given program. • Useful for comparing different implementations of the same instruction set architecture Ch.2 - The Role of Performance

  10. Using CPI Ch.2 - The Role of Performance

  11. Putting it all together Ch.2 - The Role of Performance

  12. Recess Ch.2 - The Role of Performance

  13. Evaluating Performance • WorkloadA fixed set of programs, executed under standardized conditions • BenchmarkingMeasuring performance of CPU against a specific (standardized, but possible domain specific) workload (benchmarks) Ch.2 - The Role of Performance

  14. What makes a good benchmark? • Real application • Execution spends time in diverse parts of the (source) code • Harder to “game” the evaluation (optimize the compiler/processor to perform well on benchmark) Ch.2 - The Role of Performance

  15. The SPEC benchmarks • Standard Performance Evaluation Company • SPEC2000 Integer Benchmarks • SPEC2000 Floating Point Benchmarks Ch.2 - The Role of Performance

  16. Running benchmarks • Results must be presented so as to allow for reproducibility • Include all hardware configuration details (as they can have a bearing on performance) • 1.3GHz AMD Athlon • 1.3 GHz Intel P4 Ch.2 - The Role of Performance

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