Tuning Web Performance
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Tuning Web Performance

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Tuning Web Performance Tuning Web Performance Presentation Transcript

  • Tuning Web Performance in Frontend Perspective Lin-Chieh Shangkuan (上官林傑) ericsk@gmail.com
  • AGENDA The Impacts of Web Performance Development Tools Website Optimization Concepts References
  • The Impact of Performance Longer response time from web server. Too many requests (css/javascript files, images, flashes, ...) Complicated DOM structure Inefficient JavaScript codes ....
  • The Impact of Performance Longer response time from web server. Too many requests (css/javascript files, images, flashes, ...) Complicated DOM structure Inefficient JavaScript codes 80~90% time spent on the frontend
  • Page-loading Samples
  • Development Tools Firefox http://getfirefox.com/ Firebug http://getfirebug.com/ Page Speed (Firebug plugin) http://code.google.com/speed/page-speed/ Y!Slow http://developer.yahoo.com/yslow/
  • Development Tools (cont) Chrome (Chromium/WebKit) Developer Tools http://www.chromium.org/devtools Install AMAP Latest Web Browsers e.g. IE8/9 (preview), Firefox 3.6/nightly, Safari 4/WebKit, Chrome/Chromium, Opera 10/10.5
  • Firebug Console Debugging your JavaScript code. Use console object in your JavaScript code. Interactive in the console tab.
  • Requests Analysis Analyzing the requests.
  • Listen to Suggestions Follow the suggestions from PageSpeed (or Y!Slow)
  • Chromium Devtools
  • HTTP Overviews Request: GET /foo/bar.js HTTP/1.1 Host: example.com User-Agent: Mozilla/5.0 Response: HTTP/1.1 200 OK Content-Type: application/x-javascript Last-Modified: Mon, 15 Mar 2010 10:00:00 GMT Content-Length: 1234 (function(){ .....
  • HTTP Reuqest Example $ telnet ajax.googleapis.com 80 Trying 74.125.153.95... Connected to googleapis-ajax.l.google.com. Escape character is '^]'. GET /ajax/libs/jquery/1.4.2/jquery.min.js HTTP/1.1 Host: ajax.googleapis.com User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; zh-TW; rv:1.9.2) Gecko/20100115 Firefox/3.6 GTB7.0 Accept-Encoding: gzip,deflate HTTP/1.1 200 OK Content-Type: text/javascript; charset=UTF-8 Last-Modified: Mon, 15 Feb 2010 23:30:12 GMT Date: Mon, 15 Mar 2010 08:39:18 GMT Expires: Tue, 15 Mar 2011 08:39:18 GMT Vary: Accept-Encoding X-Content-Type-Options: nosniff Server: sffe Content-Encoding: gzip Cache-Control: public, max-age=31536000 Age: 2497 Content-Length: 24678 X-XSS-Protection: 0 ;iw?F???+??m?@ə???v?I։/M???6???????$e???...
  • Ways to Speed up the Website Optimize the backend processing e.g., PHP engine, database, .... Scaling Transfers Co-location, CDN, ... Reducing the browser's requests CSS sprites, expire headers, http compression... Optimizing the contents Defer loading, rearrangement, ... Efficient JavaScript development Improving the programming techs, ...
  • Scaling Transfers Use CDN e.g., Akamai, Amazon S3, ... Pixnet experience: http://www.slideshare.net/gslin/using-cdn- to-improve-performance Reduce DNS Lookups Keep-Alive fewer domains Avoid Redirects Use Comet
  • Scaling Transfers Sharding Dominant Domains browser HTTP/1.1 HTTP/1.0 IE6, 7 2 4 IE8 6 6 FF2 2 8 FF3 6 6 Saf 4 4 Chrome 6 6 Op 4 4 Connections per server
  • Reducing Requests
  • HTTP Compression Modern browsers support HTTP compression -- to reduce the size of response content Gzip the static (html, css, js, ...) files Don't compress everything (e.g., jpg, png, pdf, ... they are already compressed) Check if the Accept-Encoding header has gzip or deflate value. Respond Content-Encoding: gzip header.
  • HTTP Compression In Apache httpd server, use mod_gzip (httpd 1.3) or mod_deflate (httpd 2.x). [mod_deflate] AddOutputFilterByType DEFLATE text/html text/css application/x-javascript Problems: Proxy may cache uncompressed content Add Vary: Accept-Encoding header IE6 bug: Q312496, Q313712
  • Make Fewer Requests CSS Sprites: Combine N icons into 1 bigger image. Reduce N requests info 1 request. Be careful of the arrangement of the icons sample: http://www.google.com.tw/images/nav_logo8.png tool: http://tw.spritegen.website-performance.org/ http://csssprites.com/ Combine CSS/JavaScript files Using Google Closure Compiler Apache: http://code.google.com/p/modconcat/ Lighttpd: http://code.google.com/p/lighttpd-mod-concat/ YUI Comobo Handler: http://yuiblog. com/blog/2008/07/16/combohandler/
  • Make Fewer Requests Reduce Cookie size (or split domains) Inline images: using base64 encoding <img src="data:image/png;base64, xxxxx"> IE7/6 doesn't support this feature Useful in mobile browser Not only images: <frame src="data:text/html,%3Chtml%3E% 3Cbody%20style%3D%22background..."></frame>
  • Using Expires Headers Use Expires header to tell the browser how long to keep the resource. Browser won't fetch the resource again until the expire time Apache mod_expires module can help setting expire time <FilesMatch ".(css|js|jpg|png)$"> ExpiresDefault "access plus 1 year" </FilesMatch> e.g., Expires: Fri, 25 Mar 2011 08:00:00 GMT Cache-Control header In stead of using a specified date, Cache-Control header shows HOW LONG the client should keep it e.g., Cache-Control: max-age=31536000 # cache 1 year
  • Using Last-Modified Headers Use Last-Modified header to tell the browser the last modified time of the resource. [request] [request] GET /foo/bar.css HTTP/1.1 GET /foo/bar.css HTTP/1.1 .... ... If-Modified-Since: Thu, 25 Mar 2010 [response] 10:00:00 GMT HTTP/1.1 200 OK ... Content-Type: text/css Last-Modified: Thu, 25 Mar 2010 10: [response] 00:00 GMT+8 HTTP/1.1 304 Not Modified .... ... (empty response body)
  • Configuring ETag ETag (Entity Tag) header tells browser which to cache How ETag works: read Wikipedia Problem: Not-the-same tag across different servers Apache: inode-size-timestamp IIS: timestamp:changenumber Solution: Set ETag manually Remove it. (in Apache) FileETag none
  • Invalidates the Cached Resources If the static resources are cached, how to invalidate them? Use signature in filename ( /js/foo.AB32FDC.js ) Add query string ( /js/foo.js?20100325110000 )
  • Optimizing Loadings
  • Minifying JavaScript Reduce the size of JavaScript files. Reduce the total response sizes. HTML, CSS files can be also compressed. Closure-compiler Web-based http://closure-compiler.appspot.com/ RESTful API http://code.google.com/closure/compiler/docs/api-ref.html Standalone executable Ofuscation Reduce the length of variables names Be careful the obfuscation method (e.g., eval cause performance degradation) Be careful the conflicts.
  • Optimizing Images Using appropriate image format and remove redundant chunks in the image files. PNG8 (256 colors) is a good choice. Optimizing: Crushing PNGs pngcrush (http://pmt.sf.net/pngcrush/) Stripping JPEG metadata jpegtran (http://jpegclub.org/) Convert GIF to PNG ImageMagick Optimizing GIF animations gifsicle ( (http://www.lcdf.org/gifsicle/) Avoid image scaling
  • Put Stylesheets on The Top Browser delays showing any visible components while it and user wait for the stylesheet at the bottom. Use <link> to include stylesheets @import MUST precede all other rules @import may cause blank white screen phenomenon (in IE)
  • Put JavaScripts at The Bottom JavaScript blocks parallel downloads Put at top: the other components are delayed- loaded. defer attributes: Firefox still blocks other downloads
  • Non-blocking Loading Scripts IE8 is the first browser that supports downloading scripts in parallel. Ways to load JavaScripts XHR Eval XHR Inject Script in iframe Inserting script DOM element document.write
  • Non-blocking Loading Scripts Existing Busy Preserve Tech Parallel Diff Domain Scripts indicator Order Normal IE8, SF4 Y Y IE, SF4 IE, SF4 XHR Eval * N N SF, Ch XHR Injection * N Y SF, Ch Script in iframe * N N IE, FF, SF, Ch Script DOM * Y Y FF, SF, Ch FF, Op IE, SF4, Ch2, Script Defer Y Y * * FF3.1 IE, SF4, Ch2, document.write Y Y * * Op
  • iframes iframes are heavy and block onload event. Use script DOM injection to insert ADs instead of iframes.
  • Efficiency Practices
  • Make JavaScript/CSS External Reusing components Cache the files Unobstrusive JavaScripts
  • Simplifying CSS Selectors CSS selector policy: Rightmost-First Tips: Avoid * selector Don't qualify ID/CSS selectors Specific rules Avoid descendant selectors Avoid Tag > Child selectors Rely on inheritance
  • Efficient JavaScript Tips Using className instead of modifying style attributes of a DOM element. [bad ] var foo = document.getElementById('foo'); foo.style.color = '#f00'; foo.style.fontWeight = 'bold'; [good] .highlight { color: #f00; font-weight: bold; } foo.className = 'highlight';
  • Efficient JavaScript Tips (con'd) Appending a newly-created DOM element after modifying its attributes. (avoid reflows) [bad] var foo = document.createElement('div'); document.body.appendChild(foo); foo.innerHTML = 'Hello, world'; foo.className = 'hello'; [good] var foo = document.createElement('div'); foo.innerHTML = 'Hello, world'; foo.className = 'hello'; document.body.appendChild(foo);
  • Efficient JavaScript Tips Using document fragment to create new contents. [bad] document.body.appendChild(createDivElement()); document.body.appendChild(createDivElement()); ... [good] var frag = document.createDocumentFragment(); frag.appendChild(createDivElement()); frag.appendChild(createDivElement()); .... document.body.appendChild(frag);
  • Efficient JavaScript Tips Using array join instead of directly concatenate strings. [bad ] ] var a = 'Hel'; a += 'lo'; a += ', wor'; a += 'ld!'; [good] var buf = ['Hel']; buf.push('lo'); buf.push(', wor'); buf.push('ld!'); a = buf.join('');
  • Efficient JavaScript Tips Faster trim method: (use simple regular expression) [bad] str.replace(/^s+|s+$/g, ''); [better] str.replace(/^s+/, '').replace(/^s+$/, ''); [much better] str = str.replace(/^s+/, ''); for (i = str.length - 1; i >=0; i--) { if (/S/.test(str.charAt(i))) { str = str.substring(0, i + 1); break; } }
  • Efficient JavaScript Tips Use popular JavaScript frameworks. (e.g. jQuery)
  • Misc.
  • Responsive Web Applications Prefetching resources AJAX Avoid long-running scripts
  • HTML5 http://whatwg.org/html5 Short tags: <!DOCTYPE html> <meta charset="UTF-8"> <script src="xxx.js">, <style>...</style> <script async ...> Application Cache (offline data) https://developer.mozilla.org/En/Offline_resources_in_Firefox http://www.whatwg.org/specs/web-apps/current- work/multipage/offline.html http://googlecode.blogspot.com/2009/04/gmail-for-mobile- html5-series-using.html WebStorage/WebDatabase API
  • Mobile Web Mobile device has lower hardware-profile so that the web performance is more important! iPhone Safari/Android browser/Opera Mini likes HTML5 (w/ a little CSS3)
  • References
  • Books High Performance Web Sites, O'Reilly Even Faster Web Sites
  • Websites Let's Make the Web Faster (Google) http://code.google.com/speed Exceptional Performance (Yahoo!) http://developer.yahoo.com/performance/ High Performance Web Sites Blog http://www.stevesouders.com/blog/