Assessing and Understanding Performance B. Ramamurthy Chapter 4

Defining Performance AirplanePassenger Capacity Cruising Range Cruising Speed (mph) Passenger throughput (passengers X mph) Boeing ,750 Boeing ,700 Concorde ,200 DC ,424

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

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

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

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