Speed is Essential for a Great Web Experience
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Andy Davies' slides fra Digicures web performance seminar på Bella Sky, 24. oktober 2012. Den engelske ekspert og freelance konsulent, Andy Davies, har været bidt af emnet om god web performance siden 90'erne. Andy hjælper virksomheder med at måle, analysere og forbedre performance og stabiliteten af deres websites. Selvom hastighed er vigtig for en god online oplevelse, bliver det ofte overset. Andy Davies vil fortælle hvordan hastighed påvirker brugeroplevelsen på et website og afdække hvordan hastighed kan måles og analyseres.
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Speed is Essential for a Great Web Experience
- 1. Speed is Essential for a Great Web Experience @andydavies Digicure Oct 2012 http://www.flickr.com/photos/ahockley/3576838608
- 2. Performance isn’t always a priority http://www.flickr.com/photos/randomidea/247994072
- 3. “Has it loaded yet?” http://www.flickr.com/photos/kindofindie/4099768084
- 4. Our perception of response time Instant Seamless Yawn! 100ms 1s 10s Response Time in Man-computer Conversational Transactions Robert B. Miller, 1968
- 5. Our perception of response time Instant Seamless Yawn! 100ms 1s 10s 3s - Recommended 6.5s - Alexa 2000 Load Time Fall 2012 Response Time in Man-computer Conversational Transactions Robert B. Miller, 1968
- 6. “50% more concentration when using badly performing web sites” Foviance http://www.flickr.com/photos/yourdon/3366991042
- 7. Effect of delay on abandonment rate... Abandonment rate over 200+ sites / 177+ million page views over 2 weeks - http://www.measureworks.nl / Gomez
- 8. Bing did some experiments +1s $/ - 2.8% +
- 9. Wallmart made some improvements -1s +2%
- 10. Shopzilla cut page load time by 5 seconds! +12% +25% -50% $$$ http://velocityconf.com/velocity2009/public/schedule/detail/7709
- 11. Measuring page load time... http://www.flickr.com/photos/wwarby/7109538317
- 12. Synthetic Monitoring 4 3 Response Time (s) 2 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 16 27 28 29 30 September 2012
- 13. But these aren’t our visitors… http://www.flickr.com/photos/br1dotcom/4297736794
- 14. These are our visitors http://www.flickr.com/photos/yourdon/2681687374
- 15. Measure Real Users’ Experience 27% Visitors (%) 13% 8% 8% 6% 6% 3% 3% 2% 1% 1 2 3 4 5 6 7 8 9 10 Load Time (s)
- 16. Measure Real Users’ Experience 27% 24% Visitors (%) 13% 8% 8% 6% 6% 3% 3% 2% 1% 1 2 3 4 5 6 7 8 9 10 > 10 Load Time (s)
- 17. Measuring Real Users - Google Analytics Relies on Navigation Timing API, can add extra timing calls to page
- 18. Looking Deeper http://www.flickr.com/photos/ohhector/3149051855
- 19. webpagetest.org
- 22. Bigger, Faster Servers? http://www.flickr.com/photos/getbutterfly/6317955134
- 23. 80% plus of page load time is on front-end Backend news.bbc.co.uk Frontend ebay.co.uk debenhams.co.uk direct.gov.uk amazon.co.uk mumsnet.com guardian.co.uk 0 1.25 2.5 3.75 5 Measured on residential ADSL line using Chrome 19
- 24. Fix slow server responses first 4 seconds!
- 25. Bandwidth (often) isn’t the bottleneck 2.0 1.5 1.0 0.5 0s 5s 10s news.bbc.co.uk tested via webpagetest.org throttled at 1.5Mbps (bursts over 1.5Mbps are artefact of testing)
- 26. “More Bandwidth Doesn’t Matter (much)” Mike Belshe 3.11s Page Load Time 1.95s 1.63s 1.50s 1.44s 1.41s 1.39s 1.38s 1.37s 1.36s 1 2 3 4 5 6 7 8 9 10 Bandwidth (Mbps)
- 27. Impact of Latency 4 3 Page Load Time (s) 2 1 0 20 40 60 80 100 120 140 160 180 200 220 240 Round Trip Time (ms)
- 28. Minimum round trips to download a file (TCP Segments) 285kB 214kB 143kB 71kB Size 1 2 3 4 5 6 7 8 9 10 11 Round Trips TCP and the Lower Bound of Web Performance John Rauser
- 29. Going Faster… http://www.flickr.com/photos/mikebaird/2464769129/
- 30. Put your pages on a diet http://www.flickr.com/photos/europedistrict/4537909259
- 31. Cut down number of HTTP requests
- 32. Move the content closer http://www.flickr.com/photos/jamesjordan/2198988999
- 33. Organise content so it’s easy to load http://www.flickr.com/photos/jemsweb/4363548805
- 34. What’s the web made of? Images Scripts Stylesheets HTML Flash Other Composition of ‘average’ web page via httparchive.org
- 35. Images are 64% of an ‘average’ web page http://www.flickr.com/photos/zaprittsky/4520788183/
- 36. Bitmapped Images JPEG PNG GIF Optimise, Optimise, Optimise! (jpegmini, pngmini, Smush.it, ImageOptim, Gifsicle etc.)
- 37. New Devices, New Challenges... 2 x Resolution = 4 x Pixels! http://www.flickr.com/photos/roopaw/6985954465
- 38. Some Alternatives CSS SVG Fonts Watch SVG sizes not always smaller than bitmap!
- 39. Don’t block the browser... http://www.flickr.com/photos/barteko/6128499314
- 40. news.bbcimg.co.uk static.bbc.co.uk Browsers can download resources in parallel
- 41. But Sometimes... The Waterfall of Doom! 2 seconds! (nearly)
- 42. The Script Tag <script src=″…″></script>
- 43. The Script Tag <script src=″…″></script> Until the script has executed, the rendering of all elements below is blocked!
- 44. “Virgin Media Broadband ISP Users Affected by Website Routing Woes” ISP Review, May 26, 2012 Customer jcmm33 said: “Same issue here as well, been like this all day. Sites like autotrader.co.uk don’t appear to be accessible, others like the telegraph.co.uk are waiting on other components to download (content from sites like cg-global.maxymiser.com, pixel.quantserve.com).” http://www.ispreview.co.uk/index.php/2012/05/uk-virgin-media-broadband-isp-users-affected-by-website-routing-woes.html
- 45. Impact on The Telegraph… http://bit.ly/Ncy7Rd
- 46. Impact on The Telegraph… http://bit.ly/Ncy7Rd
- 47. Impact on The Telegraph… Same issue affected many other sites http://bit.ly/Ncy7Rd
- 48. Load Third Party scripts asynchronously <script type="text/javascript"> function() { var js = document.createElement('script'); js.async = true; js.src = 'myscript.js'; var e = document.getElementsByTagName('script')[0]; e.parentNode.insertBefore(js, first); })(); </script> async attribute may be option but not supported by IE & Opera
- 49. The Challenge of Mobile http://www.flickr.com/photos/cubicgarden/3281555681
- 50. Argh... My brain hurts! http://www.flickr.com/photos/corneveaux/3248566797
- 51. Don’t have to do it all by hand http://www.flickr.com/photos/simeon_barkas/2557059247
- 52. Performance isn’t just for Christmas Measure Optimise Analyse
- 53. Measure Impact on Business Goals http://www.flickr.com/photos/safari_vacation/5961260280
- 55. @andydavies andy@asteno.com http://www.slideshare.net/andydavies http://www.flickr.com/photos/auntiep/5024494612
- 56. Credits All photographs copyright original owners on flickr.com Following pictograms courtesy of The Noun Project
Editor's Notes
- Andy Davies\n\nSpecialise in making web sites faster, more reliable and helping them scale as they grow\n\nSlides complete will go on Slideshare in the next day or so\n\nIf anyone has any questions or comments feel free to send me a tweet...\n\n\n
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- How we perceive response times\n\nStrangeloop Networks research into load times of Alexia Top 2000 ecommerce sites \n - Average page load time 11.21s\n - Best 2.2x, worst 40.2s!\n - Only 13 loaded in less that 5s\n\nOur perception of load time is off:\n- Our expectation is faster\n- Perceive load time as 15% slower than reality\n- Recount experience as 35% slower\nStoyan Stefanov - Psychology of Performance\n
- Retail task - find and buy a laptop on a leading e-commerce site\nInsurance task - find and buy personal travel insurance on an insurance website. \nEEG & EOG, camera\n
- \n\nAlso people&#x2019;s perception of time is faulty... (Stoyan Stefanov, Psychology of Performance)\n - Average person perceives page takes 15% longer to load that reality\n - Will recount it as 35% longer when talking to others\n\n
- Google - 400ms delay- searches down 0.6%\nAmazon - 100 ms delay - sales down 1%\n
- Walmart2% increase in conversion rate for every 1 second reduction\n
- ShopzillaUptime 99.51% > 99.97\n\nMozillareduced load time by 2.2 secs = 60 million extra downloads / year\n\nYahootraffic went up 9% for every 400ms improvement\n\nNetflix: Reduced outbound bandwidth by 43%\n\nKerboodle: Reduced hosting costs by over &#x20AC;30,000 per year\n\n
- How many have websites?\n\nHow many think theirs is fast?\n\nHow many measure?\n
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- We are not real users...\n\n&#x201C;My own developer hardware is not representative of the real world, and will be mindful of limited hardware, poor latency, and low bandwidth situations&#x201D;\nA Front End Engineer&#x2019;s Manifesto\n@zachleat\nhttp://f2em.com/\n\nActual page load times from a real site, note huge peak of over 10 seconds\n\nMany external factors can affect page load time:\n\n- Browser\n- How they are connected ADSL / mobile / public WiFi\n- Bandwidth\n- Latency\n- Anti-virus\n- Network kit\n- etc\n\nThese factors are beyond our control but to get a true picture of page load times we must measure them in the visitors browser.\n
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- Navigation Timing API \n - Firefox 7+, IE9+, Chrome 6+, Chrome on ICS\n - NO SAFARI - OS X or iOS!!!\n\nCan script to add extra timings\n\nLow sample rate\n\nAverages!!!\n\nIncrease sample rate from 1% to 100% add:\n\n_gaq.push(['_setSiteSpeedSampleRate', 100]);\n\nPage load time data collected by default since 16th Nov 2011\n\nGood description of how it works on StackOverflow\n\n
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- Some server performance issues can be improved by throwing hardware at it e.g. faster processors, more RAM (Databases love RAM), faster disks.\n\nBut should still look at optimising the back-end as it&#x2019;s an important part of the picture e.g. DB tuning, architectures, reverse proxies etc.\n\nEven without tuning the server can still improve page load times by &#x201C;flushing early&#x201D;\n\n
- Even higher on mobile\n
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- Bursting over 1.5Mbps = Testing Artefact\n
- Mike Belshe - &#x201C;More Bandwidth Doesn&#x2019;t Matter (much)&#x201D;\n(http://www.chromium.org/spdy/More_Bandwidth_Doesn_t_Matter_2_%282%29.pdf)\n\nBandwidth - Throughput, how much can be download in a given time\nLatency - Time between making the request and receiving the response\nTCP Slow-start - new connections take time to work up to &#x2018;max&#x2019; throughput\n\nConnections aren&#x2019;t synchronous e.g. ADSL - faster download than upload, so requests are much slower (but fortunately generally smaller)\n\n\n
- Mike Belshe - &#x201C;More Bandwidth Doesn&#x2019;t Matter (much)&#x201D;\n(http://www.chromium.org/spdy/More_Bandwidth_Doesn_t_Matter_2_%282%29.pdf)\n\nBandwidth - Throughput, how much can be download in a given time\nLatency - Time between making the request and receiving the response\nTCP Slow-start - new connections take time to work up to &#x2018;max&#x2019; throughput\n\nConnections aren&#x2019;t synchronous e.g. ADSL - faster download than upload, so requests are much slower (but fortunately generally smaller)\n\n\n
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- Compress (gzip / deflate) all text based content - html, js, css, xml, json (and other uncompressed components e.g. ico)\n\nMinify JS and CSS (not everyone can get gzipped content)\n\nOptimise images: correct format + tools \n- jpg: lossy\n- png: lossless (often more efficient than gif. Photoshop screws up transparency)\n- gif:animated \n\nGreat reference for image optimisation - http://www.bookofspeed.com/chapter5.html\nhttp://jpegmini.com is a new tool for crunching jpegs, uses perceptual encoding, good results\n\nUse CSS / SVG / Canvas instead of images e.g. rounded corners\n\nLean markup\n- html: avoid DIVitis, HTML5 can be more brief\n- css: @stubornella&#x2019;s OOCSS (https://github.com/stubbornella/oocss/wiki/faq)\n\nStatic content from cookieless domains (but should CSS come from the same domain?)\n\nRemove superfluous headers\n
- Merge up\n - CSS\n - JS\n\n - CSS sprites\n - Datauri&#x2019;s\n - Pictogram fonts \n - Standard characters\n\nLazy load e.g. images\n\n
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- 64%\n
- Images form on average 59% of site content (exc video and audio) \n\nRetina displays complicate things - time for vectors / fonts?\n
- What about PNGs and transparency? - need to cover the issues\n
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- Watch CSS effects on mobile\n\nCheck size - map is actually smaller as PNG 22.7KB / SVG 108KB!\n\nFont - Heydings by Heydon Works\n
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- Also CSS and fonts - anything that can block\ncg-global.maxymiser.com\n
- What if they are slow? down? Or even blocked - country, corporate firewall etc.?\n\nStart render 3.7s vs 24.5s\n\nLoad8s vs 30.4s\n\nLateRooms, Autotrader plus many others... for three days (started on a Fri)!!!\n
- What if they are slow? down? Or even blocked - country, corporate firewall etc.?\n\nStart render 3.7s vs 24.5s\n\nLoad8s vs 30.4s\n\nLateRooms, Autotrader plus many others... for three days (started on a Fri)!!!\n
- Don&#x2019;t blindly add third party scripts to a site\n\nMany social sites now have async versions, use the latest snippet.\n\nAddThis doesn&#x2019;t - don&#x2019;t use it\n\nOpenDNS blocked Google&#x2019;s jQuery CDN!\n\nh5bp includes html5shiv from googlecode - it&#x2019;s only 1KB, quicker to load from own site\n
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- Some things can be automated e.g. compression, minification, merging, image compression plus more sophisticated optimisations.\n\nFrom plugins for Wordpress and web servers, appliances that sit in front of your server farm through to cloud-based optimisation services.\n\nOther are a little more difficult e.g. flush early, improving backed performance, asynchronous loading scripts etc.\n\nAutomation products / tools...\n\nFramework support\n Asset pipeline (Rails)\n Resources plugin (Grails)\n Webassets (Python)\n Assetic (PHP)\n\nCMS plugins\n - W3 Total Cache for Wordpress\n\nServer plugins\n - mod_pagespeed (Apache)\n - reduce requests (IIS)\n - Aptimize (IIS) (&#xA3;)\n - Webo (&#xA3;)\n\nAppliances\n - Strangeloop (&#xA3;)\n - Traditional ADCs do some of this e.g. compression\n\nCloud services\n - Strangeloop (&#xA3;)\n - Torbit (&#xA3;)\n - Blaze.io (&#xA3;)\n - Yotta (&#xA3;)\n - Google&#x2019;s PageSpeed service\n
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