Even Faster Web Sites

1. Even Faster Web Sites http://stevesouders.com/docs/oscon-20090722.ppt Disclaimer: This content does not necessarily reflect the opinions of my employer.

2. the importance of frontend performance 9% 91% 17% 83% iGoogle, primed cache iGoogle, empty cache

6. Sept 2007

7. MAKE FEWER HTTP REQUESTS • USE A CDN • ADD AN EXPIRES HEADER • GZIP COMPONENTS • PUT STYLESHEETS AT THE TOP • PUT SCRIPTS AT THE BOTTOM • AVOID CSS EXPRESSIONS • MAKE JS AND CSS EXTERNAL • REDUCE DNS LOOKUPS • MINIFY JS • AVOID REDIRECTS • REMOVE DUPLICATE SCRIPTS • CONFIGURE ETAGS • MAKE AJAX CACHEABLE 14 RULES

8. June 2009

9. Even Faster Web Sites Splitting the initial payload Loading scripts without blocking Coupling asynchronous scripts Positioning inline scripts Sharding dominant domains Flushing the document early Using iframes sparingly Simplifying CSS Selectors Understanding Ajax performance..........Doug Crockford Creating responsive web apps............Ben Galbraith, Dion Almaer Writing efficient JavaScript.............Nicholas Zakas Scaling with Comet.....................Dylan Schiemann Going beyond gzipping...............Tony Gentilcore Optimizing images...................Stoyan Stefanov, Nicole Sullivan

10. Why focus on JavaScript? Yahoo! Wikipedia eBay AOL MySpace YouTube Facebook

11. scripts block <script src="A.js"> blocks parallel downloads and rendering 9 secs: IE 6-7, FF 3.0, Chr 1, Op 9-10, Saf 3 7 secs: IE 8, FF 3.5(?), Chr 2, Saf 4

12. MSN.com: parallel scripts MSN Scripts and other resources downloaded in parallel! How? Secret sauce?! var p= g.getElementsByTagName("HEAD")[0]; var c=g.createElement("script"); c.type="text/javascript"; c.onreadystatechange=n; c.onerror=c.onload=k; c.src=e; p.appendChild(c)

13. Loading Scripts Without Blocking XHR Eval XHR Injection Script in Iframe Script DOM Element Script Defer document.write Script Tag

14. XHR Eval var xhrObj = getXHRObject(); xhrObj.onreadystatechange = function() { if ( xhrObj.readyState != 4 ) return; eval(xhrObj.responseText); }; xhrObj.open('GET', 'A.js', true); xhrObj.send(''); script must have same domain as main page must refactor script

15. 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

16. Script in Iframe <iframe src='A.html' width=0 height=0 frameborder=0 id=frame1></iframe> • iframe must have same domain as main page • must refactor script: • // access iframe from main page • window.frames[0].createNewDiv(); • // access main page from iframe • parent.document.createElement('div');

17. 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

18. Script Defer <script defer src='A.js'></script> only supported in IE (just landed in FF 3.1) script and main page domains can differ no need to refactor JavaScript

19. document.write Script Tag document.write("<script type='text/javascript' src='A.js'> <\/script>"); parallelization only works in IE parallel downloads for scripts, nothing else all document.writes must be in same script block

20. Load Scripts Without Blocking *Only other document.write scripts are downloaded in parallel (in the same script block).

21. and the winner is... XHR Eval XHR Injection Script in iframe Script DOM Element Script Defer same domains different domains Script DOM Element Script Defer no order preserve order XHR Eval XHR Injection Script in iframe Script DOM Element (IE) Script DOM Element (FF) Script Defer (IE) Managed XHR Eval Managed XHR Injection no order preserve order Script DOM Element no busy show busy Script DOM Element (FF) Script Defer (IE) Managed XHR Injection Managed XHR Eval Script DOM Element (FF) Script Defer (IE) Managed XHR Eval Managed XHR Injection no busy show busy XHR Injection XHR Eval Script DOM Element (IE) Managed XHR Injection Managed XHR Eval Script DOM Element

23. asynchronous JS example: menu.js script DOM element approach <script type="text/javascript"> var domscript = document.createElement('script'); domscript.src = "menu.js"; document.getElementsByTagName('head')[0].appendChild(domscript); var aExamples = [ ['couple-normal.php', 'Normal Script Src'], ['couple-xhr-eval.php', 'XHR Eval'], ... ['managed-xhr.php', 'Managed XHR'] ]; function init() { EFWS.Menu.createMenu('examplesbtn', aExamples); } init(); </script>

24. before after

25. Loading Scripts Without Blocking !IE *Only other document.write scripts are downloaded in parallel (in the same script block).

26. what about inlined code that depends on the script?

27. coupling techniques hardcoded callback window onload timer degrading script tags script onload

28. technique 5: script onload <script type="text/javascript"> var aExamples = [['couple-normal.php', 'Normal Script Src'], ...]; function init() { EFWS.Menu.createMenu('examplesbtn', aExamples); } var domscript = document.createElement('script'); domscript.src = "menu.js"; domscript.onloadDone = false; domscript.onload = function() { if ( ! domscript.onloadDone ) { init(); } domscript.onloadDone = true; }; domscript.onreadystatechange = function() { if ( "loaded" === domscript.readyState ) { if ( ! domscript.onloadDone ) { init(); } domscript.onloadDone = true; } } document.getElementsByTagName('head')[0].appendChild(domscript); </script> pretty nice, medium complexity

29. going beyond gzipping Tony Gentilcore, Chapter 9, Even Faster Web Sites Rule 4: Gzip Components from HPWS HTTP/1.1 • request: Accept-Encoding: gzip,deflate • response: Content-Encoding: gzip Apache 2.x: AddOutputFilterByType DEFLATE text/html text/css application/x-javascript

30. benefits of gzipping 70% reduction in transfer size not just for HTML!! • all text: JavaScript, CSS, XML, JSON • not binary: images, PDF, Flash

31. so what's the issue? 15% of your users get uncompressed responses surprize! why? old browsers? no • Netscape Navigator 3 – 0.0% • Netscape Communicator 4 – 0.1% • Opera 3.5 – 0.0% • IE <3 – 0.01% clue: most prevalent in the Middle East

32. who's stripping? proxies and anti-virus software disable compression for easier response filtering

33. what to do Thanks, Tony! see Tony's chapter in Even Faster Web Sites don't assume compression go the extra mile to reduce response size • event delegation (-5%) • relative URLs (-3%) • minify HTML, JavaScript, and CSS (-4%) • use CSS rules over inline styles (-1%) • alias long JavaScript symbol names (??)

34. homage to Open Source UA Profiler Cuzillion Episodes Hammerhead SpriteMe

36. UA Profiler • tracks browser performance traits • http://stevesouders.com/ua/ • go to the test page • your browser automatically walks through the tests (requires JS) • results recorded and shared publicly • currently 20K test results, 13K unique testers, 70 browsers • help out by running the test!

38. Cuzillion'cuz there are a zillion pages to check a tool for quickly constructing web pages to see how components interact http://stevesouders.com/cuzillion/

40. Episodes framework for timing web sites • based on JavaScript timers • works on Ajax web apps • uses window.postMessage (multiple listeners) • potential industry standard http://stevesouders.com/episodes/

41. Measuring Performance • Episodes dev box synthetic testing bucket testing real user data Hammerhead

43. Hammerheadmoving performance testing upstream • http://stevesouders.com/hammerhead/ • Firebug extension • load M URLs N times, empty & primed cache • record average & median time • add'l features: export data load time measurement modal cache clearing • combine with bandwidth throttler

45. SpriteMedon't say "bite me!#*", say "SpriteMe!" • create sprites with ease • http://spriteme.org/ • bookmarklet • sprite generator: • coolRunnings by Jared Hirsch • http://jaredhirsch.com/coolrunnings/about/ • http://bitbucket.org/jared/coolrunnings/

46. takeaways focus on the frontend run YSlow (http://developer.yahoo.com/yslow) and Page Speed! (http://code.google.com/speed/page-speed/) speed matters

47. impact on revenue +2000 ms  -4.3% revenue/user1 +400 ms  -5-9% full-page traffic2 +400 ms  -0.59% searches/user1 fastest users+50% page views3 -5000 ms +7-12% revenue4 1 http://en.oreilly.com/velocity2009/public/schedule/detail/8523 2 http://www.slideshare.net/stoyan/yslow-20-presentation 3 http://en.oreilly.com/velocity2009/public/schedule/detail/7579 4 http://en.oreilly.com/velocity2009/public/schedule/detail/7709 Bing: Yahoo: Google: AOL: Shopzilla:

48. cost savings hardware – reduced load • Shopzilla – 50% fewer servers bandwidth – reduced response size http://billwscott.com/share/presentations/2008/stanford/HPWP-RealWorld.pdf

49. if you want • better user experience • more revenue • reduced operating costs the strategy is clear Even Faster Web Sites

50. 1:00 – book signing at Barnes & Noble 3:20 – free consulting at Google booth Steve Souders souders@google.com http://stevesouders.com/docs/oscon-20090722.ppt