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  • 1. Predicting User Activity to Make The Web Fast Velocity Conference 2012 Arvind Jain and Dominic Hamon Google
  • 2. How fast is the web today?● Chrome ~ 2.3s/5.4s page load time (median/mean)● Google Analytics ~ 2.9s/6.9s page load time (median/mean)● Mobile ~ 4.3s/10.2s page load time (median/mean) http://analytics.blogspot.com/2012/04/global-site-speed-overview-how-fast-are.html
  • 3. Web page size over time http://httparchive.org/
  • 4. Making the web fast● Faster browsers● Faster networks● Faster hardware● Faster pagesBut not enough to make the web Instant...
  • 5. The time between requests● ~ 3 seconds to type a URL● ~ 15 seconds to select a search result● Plenty of idle time● Why not use it?
  • 6. Predict and Prerender● Predict user navigation or follow advice from page <link rel=prerender>● Fetch all resources for a page● Render to a hidden tab● Swap in when user navigates
  • 7. Chrome Omnibox Prerendering● Already provide suggestions to the user● Opportunity to learn browsing behaviour● Ability to develop good prediction model● Little contention for resources
  • 8. Implementation details● Track whether the user takes a suggestion● Map users text input to suggestion and hit/miss counts● Given user input and suggestion, calculate confidence C: ○ C = H / (H + M) where H is the hit count, M is the miss count
  • 9. Implementation example● User types c● Suggestions are: ○ www.cnn.com ○ comcast.net● User types n● Omnibox shows cn● Suggestion is www.cnn.com● User selects www.cnn.com
  • 10. Implementation example (cont.)● We store:{ c, { { cnn.com, 1, 0 }, { comcast.net, 0, 1 }, }, cn, { { cnn.com, 1, 0 }, },}
  • 11. Implementation example (cont.)● Over time, this data structure evolves to something like: View your data at chrome://predictors in Chrome 20
  • 12. Implementation example (cont..)● User types c● Suggestions are: ○ www.cnn.com ○ comcast.net● www.cnn.com is selected by default● Confidence is C = 1● Start prerendering www.cnn.com
  • 13. Demo
  • 14. Key results● Coverage ○ Almost a third of Omnibox navigations are prerendered● Accuracy ○ About 90% of those prerenders are used● Instant ○ Between 15% and 20% of Omnibox navigations are instant (<10 ms)● Median time saved ○ ~1 second (>40%) per Omnibox navigation
  • 15. Total time saved per day Omnibox: Over 10 years Search: Over 20 years
  • 16. Why should you care?● Your site will be prerendered at some point by some users● Check your site is compatible● Page Visibility API● Consider <link rel=prerender> for your own site https://developers.google.com/chrome/whitepapers/prerender http://prerender-test.appspot.com/
  • 17. Thank youArvind Jain and Dominic Hamon Google