L40 - CS61C Machine Structures Lecture 40 - Performance...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
CS61C L40 Performance Wawrzynek, Fall 2007 © UCB 12/3/2007 John Wawrzynek (www.cs.berkeley.edu/~johnw) www-inst.eecs.berkeley.edu/~cs61c/ CS61C – Machine Structures Lecture 40 - Performance 1 CS61C L40 Performance Wawrzynek, Fall 2007 © UCB Why do we worry about performance? As a consumer : A n application might need a certain level of performance (DOOM) want to be assured that your machine can handle it (here interested in absolute performance ), or would like to maximize the use of your dollars (here interested in performance/$). As a company selling computer systems : Y ou compete on the basis of absolute performance, performance per unit price, and increasingly, performance per unit power consumption. As a designer : F aced with many design alternatives to meet design objectives. The way to choose the best design alternative is to analyze and measure each one with regards to performance, cost, and power consumption. How do we characterize computer performance? 2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CS61C L40 Performance Wawrzynek, Fall 2007 © UCB Two Notions of “Performance” Plane Boeing 747 BAD/Sud Concorde Top Speed DC to Paris Passen- gers Throughput (passengers x mph) 610 mph 6.5 hours 470 286,700 1350 mph 3 hours 132 178,200 Which has higher performance? Interested in time to deliver 1 passenger? Or, interested in delivering as many passengers per day as possible? In a computer, time for one task called Response Time or Execution Time In a computer, tasks per unit time called Throughput or Bandwidth 3 CS61C L40 Performance Wawrzynek, Fall 2007 © UCB De±nitions F is n times faster than S ” means: If we are concerned with response time: and, “ F is n times faster than S ” means: Performance is characterized as the number of actions per unit time (throughput) or as time per action (response time). 4
Background image of page 2
CS61C L40 Performance Wawrzynek, Fall 2007 © UCB Example of Response Time vs. Throughput • Time of Concorde vs. Boeing 747? • Concord is (6.5 hours / 3 hours) faster = 2.2 times faster • Throughput of Boeing vs. Concorde? • Boeing 747: (286,700 pmph / 178,200 pmph) = 1.6 times faster • Boeing is 1.6 times (“60%”) faster in terms of throughput • Concord is 2.2 times (“120%”) faster in terms of flying time (response time) In cs61c we will focus primarily on response time not throughput. 5 CS61C L40 Performance Wawrzynek, Fall 2007 © UCB Confusing Wording on Performance We will use “n times faster”; its less confusing than “m % faster” As faster means both increased performance and decreased execution time, to reduce confusion will use improve performance ” or improve execution time 6
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
CS61C L40 Performance Wawrzynek, Fall 2007 © UCB What is Time? Straightforward de±nition of time:
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 14

L40 - CS61C Machine Structures Lecture 40 - Performance...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online