EE357Unit12_PerformanceModels(1)

EE357Unit12_Performa - Performance Analysis Which of the following airplanes has the best performance Passengers 101 470 132 146 Range(mi 630 4150

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1 © Mark Redekopp, Al rights reserved EE 357 Unit 12 Performance Modeling © Mark Redekopp, Al rights reserved Performance Analysis Airplane Passengers Range (mi) Speed (mph) Boeing 737-100 101 630 598 Boeing 747 470 4150 610 Concorde 132 4000 1350 Douglas DC-8-50 146 8720 544 Which of the following airplanes has the best performance? How much faster is the Concorde vs. the 747 How much bigger is the 747 vs. DC-8? © Mark Redekopp, Al rights reserved An Opening Question • An Intel and a Sun/SPARC computer measure their respective rates of instruction execution on the same application written in C – Computer A achieves 160 MIPS (Millions of Instructions Per Second) – Computer B achieves 200 MIPS • Which computer executes the program faster? – It depends on the instruction set and compiler (ultimately, the instruction count). Computer B and its compiler may use many more simpler (faster) instructions to implement the program thereby increasing its instruction execution rate but saying nothing of overall execution time © Mark Redekopp, Al rights reserved Another Question • A Pentium 3 has a clock rate of 1 GHz while a Pentium 4 has a clock rate of 2 GHz. – They implement the same instruction set – They are tested on the same executable program. • Is the Pentium 4 twice as fast as the Pentium 3? – Since they both use the same instructions and the same instruction count (same executable), we may think that the Pentium 4 would be twice as fast – However, the microarchitectural implementation of the processor may mean that the Pentium 3 executes instructions in 2 clocks on average while the Pentium 4 executes instruction in 4 clocks on average thus making the execution time exactly the same.
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2 © Mark Redekopp, Al rights reserved Performance and Cost • Which computer is fastest? • Not so simple – Scientific simulation – FP performance – Program development – Integer performance – Commercial workload – Memory, I/O © Mark Redekopp, Al rights reserved Defining Performance • What is important to whom? • Computer system user – Minimize elapsed time for program = time_end – time_start – Called response time • Computer center manager – Maximize completion rate = #jobs/second – Called throughput © Mark Redekopp, Al rights reserved Wall Clock Time vs. CPU Time • Even execution time can be hard to measure accurately because the OS may allocate a percentage of compute cycles to other programs (also, part of a programs execution is spent in OS calls for I/O, etc.) – Wall Clock Time: Real time it took from when the user submitted the job until it was completed – CPU Time: Actual time the program took to execute when it was running © Mark Redekopp, Al rights reserved What is Performance for us? • For computer architects
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This note was uploaded on 04/03/2011 for the course EE 357 taught by Professor Mayeda during the Spring '08 term at USC.

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EE357Unit12_Performa - Performance Analysis Which of the following airplanes has the best performance Passengers 101 470 132 146 Range(mi 630 4150

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