lec2-perf - ECE3055 Computer Architecture and Operating...

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1 ECE3055 Computer Architecture and Operating Systems Lecture 2 Performance
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2 Methodology: Measure, Report, and Summarize Make intelligent choices See through the marketing hype Key to understanding underlying organizational motivation Why is some hardware better than others for different programs? What factors of system performance are hardware related? (e.g., Do we need a new machine, or a new operating system?) How does the machine's instruction set affect performance? Performance
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3 Which of these airplanes has the best performance? Airplane Passengers Range (mi) Speed (mph) Boeing 737-100 101 630 598 Boeing 747 470 4150 610 BAC/Sud Concorde 132 4000 1350 Douglas DC-8-50 146 8720 544 How much faster is the Concorde compared to the 747? How much bigger is the 747 than the Douglas DC-8?
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4 Response Time (latency) — How long does it take for my job to run? — How long does it take to execute a job? — How long must I wait for the database query? Throughput — How many jobs can the machine run at once? — What is the average execution rate? — How much work is getting done? If we upgrade a machine with a new processor what do we increase? If we add a new machine to the lab what do we increase? Computer Performance: TIME, TIME, TIME
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5 Elapsed Time counts everything (disk and memory accesses, I/O , etc.) a useful number, but often not good for comparison purposes CPU time doesn't count I/O or time spent running other programs can be broken up into system time, and user time Our focus: user CPU time time spent executing the lines of code that are "in" our program Execution Time
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6 For some program running on machine X, Performance X = 1 / Execution time X "X is n times faster than Y" Performance X / Performance Y = n Problem: machine A runs a program in 20 seconds machine B runs the same program in 25 seconds Definition of Performance
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7 Clock Cycles Instead of reporting execution time in seconds, we often use cycles Clock “ticks” indicate when to start activities (one abstraction): cycle time = time between ticks = seconds per cycle clock rate (frequency) = cycles per second (1 Hz = 1 cycle/sec) A 200 MHz clock has a _______________ cycle time time
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So, to improve performance (everything else being equal) you can either ________ the # of required cycles for a program, or
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lec2-perf - ECE3055 Computer Architecture and Operating...

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