1. Daniel AustinGRIN Technologies, Inc.The Connected Life Companydaniel.austin@grintech.netV1.1

2. Getting Started With Web Performance Upcoming Title Change:The Definitive Guide to Web Performance Pre-release available now First 4 Chapters online at OReilly.com Full release in Dec. 2014 3. Todays Talk: QuestionsQ: What Does Performance Mean?Q: What Do Fast and Slow Mean?Q: How Fast is Fast Enough? 4. The MPPC Model of Web PerformanceT1 = Network Connection T2 = Server Duration T3 = Network Transport T4 = Client Processing 5. The User TimeSource: The Economic Value of Rapid Response Time Doherty & Thadani 1982, IBM Research 6. The Layer 8 HypothesisYou are a Node on the Internet! The Internet Connects People,Not Computers Humans are Machines that TurnData into Information 7. Hi, Whats Your Bandwidth?Source: The User Illusion Tor Norretranders 8. Optical Transmission: MK1 Eyeball Human Visual Bandwidth ~ 8.75 MBPS Not a Simple Digital System! 9. The NeoCortical Visual StackThus just ~100 ms after image photons impinge on the retina, a first wave of image-selective neuronal activityis present throughout much of The Inferior Temporal lobeHow does the brain solve visual object recognition? Dicarlo, et al Neuron. Feb 9, 2012; 73(3): 415434 10. Grokking isnt the Same as Seeing THuman = TP+TC+TM ~ 100ms to identify distinct objects ~ 150ms to respond => 250ms User think timePerceptualProcessorCognitiveProcessor 10x variabilityMotorProcessorTP ~ 100 ms [50-200ms]TC ~ 70ms [30-100ms]TM ~ 70ms [25-170ms]Source: MIT/CSAIL 11. Cognitive Processing: Choice Response Times When faced with Nchoices, users will takeO(log N) cycles to processthe data and respond.(Hick-Hyman Law) This also means that userscan process additionaltasks in constant time 12. Fitts Law and the Web The motor processing time TM is related to thesize and apparent distance of the object onthe display and is limited by accuracy 13. Fitts Law and Mobile Devices Implications for RWD Size of UI objects on small screens limits accuracy May require qualitative redesign for human motorlimitations Wearables and small devices are near the point ofminimum usability for visual interaction Are recent increases in mobile phone sizes anaccommodation to Fitts Law? 14. Test Your Own Response Time Best Scores: ~100-200ms Try it yourselfhttp://www.humanbenchmark.com/tests/reactiontime 15. The Practice EffectCan you optimize your own response time?Yes, up to a point.The Power Law of Practice indicates thatthe time required to do a task the nth timedeclines exponentially and then stabilizes.Tn = T1*n-a with a ~ 0.2-0.6 16. Browsing Fast and SlowFastTHuman > TSystemThe system waits on the userSlowTHuman < TSystemThe user waits on the system 17. Is 100ms Fast Enough? In most cases, THuman > 100ms But users are sensitive to changes ~ 30ms Client processing adds additional time User tasks often involve more than one responsestep 18. Its Fast Enough WhenIt Takes YOU Longer to Process theInformationThan It Takes to Deliver It. 19. When Its Fast Enough, Then What? Make it fast for everyone Then you can try adding more stuff to the page!But not until then! Technologies are becoming available more quicklythan we can optimize them 20. Summing Up: How Fast is Fast Enough?Its Fast Enough When You are Waiting on Your Users,Not Making Them Wait for You!Human Mental Processing is Parameterized by ~100msResponse TimesWe Cant Expect the Web to Achieve TV-level ResponseTimesUltimately, Performance Is About Respect. 21. Daniel AustinGRIN Technologies, Inc.The Connected Life Companydaniel.austin@grintech.netV1.1@daniel_b_austin@GRINTechInc