L12-Performance - Computer Performance He said, to speed...

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L12 – Performance 1 Comp 411 – Fall 2009 10/26/2009 Computer Performance He said, to speed things up we need to squeeze the clock
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L12 – Performance 2 Comp 411 – Fall 2009 10/26/2009 Helps us make intelligent design choices See through the marketing hype Key to understanding underlying computer organization Why is some hardware faster 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 a machine’s instruction set affect its performance? Why Study Performance?
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L12 – Performance 3 Comp 411 – Fall 2009 10/26/2009 Which Airplane has the Best Performance? How much faster is the Concorde than the 747? How much larger is the 747’s capacity than the Concorde? It is roughly 4000 miles from Raleigh to Paris. What is the throughput of the 747 in passengers/hr? The Concorde? What is the latency of the 747? The Concorde? Airplane Passengers Range (mi) Speed (mph) Boeing 737-100 132 630 598 Boeing 747 470 4150 610 BAC/Sud Concorde 101 4000 1350 Douglas DC-8-50 146 8720 544 2.213 X 4.65 X 675 . 71 4000 610 470 = × 0875 . 34 4000 1350 101 = × 6.56 hours, 2.96 hours passengers/hr pass hr
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L12 – Performance 4 Comp 411 – Fall 2009 10/26/2009 Latency: Clocks from input to corresponding output — How long does it take for my program to run? — How long must I wait after typing return for the result? Throughput: How many results per clock — How many results can be processed per second? — What is the average execution rate of my program? Performance Metrics Latency Throughput
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L12 – Performance 5 Comp 411 – Fall 2009 10/26/2009 Design Tradeoffs Minimum Cost : measured by the size of the circuit. 0 1 0 1 Best Performance/Price : measured by the ratio of MIPS to size. In power-sensitive applications MIPS/ Watt is important too. Maximum Performance : measured by the numbers of instructions executed per second
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L12 – Performance 6 Comp 411 – Fall 2009 10/26/2009 Elapsed Time/Wall Clock Time counts everything (disk and memory accesses, I/O , etc.) a useful number, but often not good for comparison purposes CPU time Doesn’t include I/O or time spent running other programs can be broken up into system time, and user time Our focus: user CPU time Execution Time
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L12 – Performance 7 Comp 411 – Fall 2009 10/26/2009 For some program running on machine X, Performance X = Program Executions / Time X (executions/ sec) "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 Book's Definition of Performance Performance A = 1/20 Performance B = 1/25 Machine A is (1/20)/(1/25) = 1.25 times faster than Machine B
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L12 – Performance 8 Comp 411 – Fall 2009
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This note was uploaded on 10/31/2009 for the course COMPUTER computer 1 taught by Professor Abedauthman during the Spring '08 term at Aarhus Universitet.

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L12-Performance - Computer Performance He said, to speed...

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