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Speed is Essential for a Great Web Experience
 

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. ...

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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  • 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’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 €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“My own developer hardware is not representative of the real world, and will be mindful of limited hardware, poor latency, and low bandwidth situations”\nA Front End Engineer’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’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 “flushing early”\n\n
  • Even higher on mobile\n
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  • Bursting over 1.5Mbps = Testing Artefact\n
  • Mike Belshe - “More Bandwidth Doesn’t Matter (much)”\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 ‘max’ throughput\n\nConnections aren’t synchronous e.g. ADSL - faster download than upload, so requests are much slower (but fortunately generally smaller)\n\n\n
  • Mike Belshe - “More Bandwidth Doesn’t Matter (much)”\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 ‘max’ throughput\n\nConnections aren’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’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’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’t blindly add third party scripts to a site\n\nMany social sites now have async versions, use the latest snippet.\n\nAddThis doesn’t - don’t use it\n\nOpenDNS blocked Google’s jQuery CDN!\n\nh5bp includes html5shiv from googlecode - it’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) (£)\n - Webo (£)\n\nAppliances\n - Strangeloop (£)\n - Traditional ADCs do some of this e.g. compression\n\nCloud services\n - Strangeloop (£)\n - Torbit (£)\n - Blaze.io (£)\n - Yotta (£)\n - Google’s PageSpeed service\n
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Speed is Essential for a Great Web Experience Speed is Essential for a Great Web Experience Presentation Transcript