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You've been asked to investigate why your web site is loading slowly. You've heard of WebPagetest.org so you enter the URL and run a test. What appears next is a colorful chart that looks like a Dr. Seuss illustration. Some bars are long, some are short. Some bars are blue, some are green. "That's nice," you say to yourself, wondering what to do next. It looks benign, innocently simple. But you know it holds many secrets. The waterfall chart is a mysterious force to some developers. Performance gurus seem to be able to divine the ailments of a slow site at one quick glance. "How?" you wonder. The reality is that anyone can read a waterfall chart - if they know that they are looking for. This presentation will bestow upon you the ability to recognize specific patterns in a waterfall chart, patterns which are the signs of a slow site. Using these newfound skills, you will become that performance guru and everyone will rejoice. Presented on Google Developers Live on June 13, 2013. https://developers.google.com/live/shows/779042419
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Waterfall AntiPatterns
Google Developers LiveJune 13, 2013
Rick ViscomiWeb Developer, YouTube
Web Performance
1 2 3 4 5 6 7 8 9
9 runs
Median Selection
1 2 3 4 5 6 7 8 9 10
10 runs
1 2 3 4 5 6 7 8 9
9 runs
Median Selection
1 2 3 4 5 6 7 8 9 10
10 runs
Waterfall AntiPatterns
Anatomy of a Request
● DNS Lookup● Initial Connection● SSL Negotiation● TTFB● Content Download
HTTP Responses: Redirects
● 301 Moved Permanently● 302 Found
HTTP Responses: Not Modified
● Conditional GET
● Cache static content with long TTL○ Cache-Control: max-age=31536000
Last-Modified: Thu, 13 Jun 2013 15:17:34 GMT
● Cache busting○ style_20130614.css
HTTP Responses: Errors
● 404 Not Found
Extra Credit: What happened here?
Canceled Requests
Internet Explorer only »
Navigation Timing
● domContentLoaded* (document.ready)● Start Render (first paint)● loadEvent* (onload)● Document Complete (loadEventStart)* Chrome and Firefox only
Navigation Timing
Navigation Timing
Navigation Timing
Request Serialization
● "stair step" pattern
● many requests
● few connections○ 2 - 6
● HTTP 2.0?
Request Serialization
Connection View
cssjavascriptimagesflash
Request Serialization
Connection View
cssjavascriptimagesflash
Closed Connections
● TCP overhead
● Enable Keep-Alive
≈
Network Silence
● bandwidth utilization low
● CPU utilization high○ why?
Demo
Summary
● waterfall slope● request components● HTTP responses
○ redirects○ conditional GETs○ errors
● page load events● request concurrency● network utilization
Preview: Worst of WebPagetest
● 46 requests○ 5 successful
● 21 seconds to Start Render
● 30% gzip savings
www.aplia.com
Preview: Worst of WebPagetest
● 443 requests
● 8,000 DOM elements
● 1.6 MB of JavaScript
● 75 unique domains
coder143.com
Preview: Worst of WebPagetest
● 2 MB page weight
● 26 second load time
● 17 second repeat view
www.taboradelaide.edu.au/
Preview: Worst of WebPagetest
● 1.4 seconds to first byte
● 4.3 seconds of orange
● 84% images or JS
comoeliminarlasestrias.org
Further Reading
High PerformanceBrowser Networking
Ilya Grigorik
WPT Documentation● sites.google.com/.../docs/
Make the Web Faster● developers.google.com/speed/
Planet Performance● perfplanet.com
Thank You
Rick [email protected]+Rick Viscomi@rick_viscomi
Hands-OnWeb Performance
Optimization Workshop
Coming Soon:
June 18, 2013Santa Clara, CA
