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Assessing and Understanding Performance

Assessing and Understanding Performance. B. Ramamurthy Chapter 4. Defining Performance. Measuring Performance. Time: elapsed time, response time Clock rate.. Clock cycles: events in the system takes place precisely according to a clock that runs at constant time. CPU execution time =

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Assessing and Understanding Performance

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  1. Assessing and UnderstandingPerformance B. Ramamurthy Chapter 4

  2. Defining Performance

  3. Measuring Performance • Time: elapsed time, response time • Clock rate.. Clock cycles: events in the system takes place precisely according to a clock that runs at constant time. • CPU execution time = CPU clock cycle for a program X Clock cycle time

  4. Improving Performance • A program runs in 10 seconds on computer A, which has a 4 Ghz clock. We want to build another computer B that will run program in 6 seconds. We can increase the clock rate of , but this affects the number of clock cycles of B and it is now 1.2 times that of B. What is the clock rate of B? • CPU clock cycles = instructions X average clock cycles per instructions

  5. Performance Equation • CPU Time = CPU Clock cycles X Clock cycle Time • = Inst. Count X CPI X Clock cycle time • = (Inst. Count X CPI ) /clock rate • Algorithm affects instruction count • Programming language affects instruction count and CPI • Compiler: instruction count and CPI • Instruction set architecture: Instruction count, clock rate, CPI • Lets look at the examples in pages 252, 253

  6. SPEC Benchmarks • System Performance Evaluation Corporation (SPEC) • Latest release is a suite of programs: 12 integer and 14 floating point programs • CINT and CFP measure the geometric means of the performances of the CPU for the benchmarks. • See Figure 4.5 • SPECweb99 a throughput benchmark for Web Servers

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