Oscon 20080724


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  • Permission to use photo given by Amnemona: http://www.flickr.com/photos/marinacvinhal/379111290/
  • Oscon 20080724

    1. 1. Steve Souders [email_address] http://stevesouders.com/ Even Faster Web Sites best practices for faster pages Disclaimer: This content does not necessarily reflect the opinions of my employer.
    2. 2. The Importance of Frontend Performance 17% 83% iGoogle, primed cache 9% 91% iGoogle, empty cache
    3. 3. Time Spent on the Frontend Empty Cache Primed Cache www.aol.com 97% 97% www.ebay.com 95% 81% www.facebook.com 95% 81% www.google.com/search 47% 0% search.live.com/results 67% 0% www.msn.com 98% 94% www.myspace.com 98% 98% en.wikipedia.org/wiki 94% 91% www.yahoo.com 97% 96% www.youtube.com 98% 97%
    4. 4. The Performance Golden Rule 80-90% of the end-user response time is spent on the frontend. Start there. greater potential for improvement simpler proven to work
    5. 5. 14 Rules <ul><li>Make fewer HTTP requests </li></ul><ul><li>Use a CDN </li></ul><ul><li>Add an Expires header </li></ul><ul><li>Gzip components </li></ul><ul><li>Put stylesheets at the top </li></ul><ul><li>Put scripts at the bottom </li></ul><ul><li>Avoid CSS expressions </li></ul><ul><li>Make JS and CSS external </li></ul><ul><li>Reduce DNS lookups </li></ul><ul><li>Minify JS </li></ul><ul><li>Avoid redirects </li></ul><ul><li>Remove duplicate scripts </li></ul><ul><li>Configure ETags </li></ul><ul><li>Make AJAX cacheable </li></ul>
    6. 6. High Performance Web Sites YSlow
    7. 7. <ul><li>http://conferences.oreilly.com/velocity/ </li></ul>June 22-24, 2009
    8. 8. High Performance Web Sites, Vol 2 <ul><li>Split the initial payload </li></ul><ul><li>Load scripts without blocking </li></ul><ul><li>Don't scatter inline scripts </li></ul><ul><li>Split dominant domains </li></ul><ul><li>Make static content cookie-free </li></ul><ul><li>Reduce cookie weight </li></ul><ul><li>Minify CSS </li></ul><ul><li>Optimize images </li></ul><ul><li>Use iframes sparingly </li></ul><ul><li>To www or not to www </li></ul>
    9. 9. Why focus on JavaScript? AOL eBay Facebook MySpace Wikipedia Yahoo! YouTube
    10. 10. Scripts Block <script src=&quot;A.js&quot;> blocks parallel downloads and rendering What's &quot;Cuzillion&quot;? http://stevesouders.com/cuzillion/?ex=10008
    11. 11. Cuzillion 'cuz there are a zillion pages to check a tool for quickly constructing web pages to see how components interact Open Source http://stevesouders.com/cuzillion/
    12. 12. Initial Payload and Execution 26% avg 252K avg JavaScript Functions Executed before onload www.aol.com 115K 30% www.ebay.com 183K 44% www.facebook.com 1088K 9% www.google.com/search 15K 45% search.live.com/results 17K 24% www.msn.com 131K 31% www.myspace.com 297K 18% en.wikipedia.org/wiki 114K 32% www.yahoo.com 321K 13% www.youtube.com 240K 18%
    13. 13. Split the initial payload split your JavaScript between what's needed to render the page and everything else load &quot;everything else&quot; after the page is rendered separate manually (Firebug); tools needed to automate this (Doloto from Microsoft) load scripts without blocking – how?
    14. 14. MSN.com: Parallel Scripts Scripts and other resources downloaded in parallel! How? var p= g.getElementsByTagName(&quot;HEAD&quot;)[0]; var c=g.createElement(&quot;script&quot;); c.type=&quot;text/javascript&quot;; c.onreadystatechange=n; c.onerror=c.onload=k; c.src=e; p.appendChild(c) MSN
    15. 15. Advanced Script Loading XHR Eval XHR Injection Script in Iframe Script DOM Element Script Defer document.write Script Tag
    16. 16. XHR Eval script must have same domain as main page must refactor script var xhrObj = getXHRObject(); xhrObj.onreadystatechange = function() { if ( xhrObj.readyState != 4 ) return; eval(xhrObj.responseText); }; xhrObj.open('GET', 'A.js', true); xhrObj.send(''); http://stevesouders.com/cuzillion/?ex=10009
    17. 17. XHR Injection var xhrObj = getXHRObject(); xhrObj.onreadystatechange = function() { if ( xhrObj.readyState != 4 ) return; var se=document.createElement('script'); document.getElementsByTagName('head') [0].appendChild(se); se.text = xhrObj.responseText; }; xhrObj.open('GET', 'A.js', true); xhrObj.send(''); script must have same domain as main page http://stevesouders.com/cuzillion/?ex=10015
    18. 18. Script in Iframe <iframe src='A.html' width=0 height=0 frameborder=0 id=frame1></iframe> <ul><li>iframe must have same domain as main page </li></ul><ul><li>must refactor script: </li></ul><ul><ul><li>// access iframe from main page </li></ul></ul><ul><ul><li>window.frames[0].createNewDiv(); </li></ul></ul><ul><ul><li>// access main page from iframe </li></ul></ul><ul><ul><li>parent.document.createElement('div'); </li></ul></ul>http://stevesouders.com/cuzillion/?ex=10012
    19. 19. Script DOM Element var se = document.createElement('script'); se.src = 'http://anydomain.com/A.js'; document.getElementsByTagName('head') [0].appendChild(se); script and main page domains can differ no need to refactor JavaScript http://stevesouders.com/cuzillion/?ex=10010
    20. 20. Script Defer <script defer src='A.js'></script> only supported in IE script and main page domains can differ no need to refactor JavaScript http://stevesouders.com/cuzillion/?ex=10013
    21. 21. document.write Script Tag document.write (&quot;<scri&quot; + &quot;ipt type='text/javascript' src='A.js'>&quot; + &quot;</scri&quot; + &quot;ipt>&quot;); parallelization only works in IE parallel downloads for scripts, nothing else all document.write s must be in same script block http://stevesouders.com/cuzillion/?ex=10014
    22. 22. Browser Busy Indicators
    23. 23. Browser Busy Indicators good to show busy indicators when the user needs feedback bad when downloading in the background
    24. 24. Ensure/Avoid Ordered Execution <ul><li>Ensure scripts execute in order: </li></ul><ul><ul><li>necessary when scripts have dependencies </li></ul></ul><ul><ul><li>IE: http://stevesouders.com/cuzillion/?ex=10017 </li></ul></ul><ul><ul><li>FF: http://stevesouders.com/cuzillion/?ex=10018 </li></ul></ul><ul><li>Avoid scripts executing in order: </li></ul><ul><ul><li>faster – first script back is executed immediately </li></ul></ul><ul><ul><li>http://stevesouders.com/cuzillion/?ex=10019 </li></ul></ul>
    25. 25. Summary of Traits * Only other document.write scripts are downloaded in parallel (in the same script block).
    26. 26. and the winner is...
    27. 27. Load Scripts without Blocking <ul><li>don't let scripts block other downloads </li></ul><ul><li>you can still control execution order, busy indicators, and onload event </li></ul><ul><li>What about inline scripts? </li></ul>
    28. 28. Inline Scripts Block <ul><li>long executing inline scripts block rendering and downloads </li></ul><ul><li>http://stevesouders.com/cuzillion/?ex=10035 </li></ul><ul><li>workarounds: </li></ul><ul><ul><li>initiate execution with setTimeout (>250 for FF, nglayout.initialpaint.delay ) </li></ul></ul><ul><ul><li>move JavaScript to external script with advanced downloading techniques </li></ul></ul><ul><ul><li>use Defer attribute (IE only) </li></ul></ul>
    29. 29. Inline Scripts after Stylesheets Block Downloading <ul><li>Firefox blocks parallel downloads when downloading stylesheets </li></ul><ul><li>IE doesn't... </li></ul><ul><li>...unless the stylesheet is followed by an inline script </li></ul><ul><li>http://stevesouders.com/cuzillion/?ex=10021 </li></ul><ul><li>best to move inline scripts above stylesheets or below other resources </li></ul><ul><li>use Link, not @import </li></ul>
    30. 30. Examples of Scattered Scripts eBay MSN MySpace Wikipedia
    31. 31. Don't Scatter Inline Scripts remember inline scripts carry a cost avoid long-executing inline scripts don't put inline scripts between stylesheets and other resources
    32. 32. Takeaways <ul><li>focus on the frontend </li></ul><ul><li>run YSlow: http://developer.yahoo.com/yslow </li></ul><ul><li>this year's focus: JavaScript </li></ul><ul><ul><li>Split the Initial Payload </li></ul></ul><ul><ul><li>Load Scripts without Blocking </li></ul></ul><ul><ul><li>Don't Scatter Inline Scripts </li></ul></ul><ul><li>speed matters </li></ul><ul><li>you CAN make your site even faster! </li></ul>
    33. 33. Announcement 1: HTTPWatch for FF <ul><li>http://httpwatch.com/ </li></ul><ul><li>previously IE only </li></ul><ul><li>Firefox private beta now </li></ul><ul><li>Firebug 1.05 Net Panel buggy </li></ul>
    34. 34. Announcement 2: Firebug Lite 1.2 <ul><li>http://getfirebug.com/lite.html </li></ul><ul><li>console.log </li></ul><ul><li>Inspect </li></ul><ul><li>DOM and CSS </li></ul>
    35. 35. Announcement 3: Mozilla & Firebug <ul><li>John Resig, Rob Campbell, Jan Odvarko </li></ul><ul><li>Firebug Working Group </li></ul><ul><li>stability, performance, bug fixes </li></ul>
    36. 36. Steve Souders [email_address] http://stevesouders.com/