Optimizing Your Frontend Performance

Optimizing Your
Frontend Performance
Thomas Weinert

About Me
 Application Developer
▹ PHP
▹ XSLT/XPath
▹ (some) Javascript

papaya CMS
▹ PHP based Content Management System
▹ uses XSLT for Templates

Thomas Weinert, papaya Software GmbH

How to scale you webpage?
 Hardware
 Backend

Frontend


Hardware
 More hardware
 Better hardware

Moores Law
▹ Transistors doubling every 18 months
▹ Transistors != Performance
 Distributed systems are complex
 Think about environment


Backend
 External data sources are slow
▹ SQL
▹ Files
▹ Network

Locking is slower

Memory is faster
▹ but less secure


Mini/Micro Optimisations
 Myths
▹ echo vs. print
▹ ' vs. quot;

Objects vs. functions vs. linear source

Template systems


Mini/Micro Optimisations

DON'T DO IT


Yahoo!
 Yahoo!'s Exceptional Performance team
▹ Yahoo!'s Exceptional Performance team evangelizes
best practices for improving web performance.
They conduct research, build tools, write articles
and blogs, and speak at conferences. Their best
practices center around the rules for high
performance web sites.
▹ http://developer.yahoo.com/performance/


Results
 80% of the end-user response time is spent on
the front-end.


Firebug
 Firefox extension
 Analyze and manipulate
▹ requests, page structure, CSS

Javascript debugger


YSlow
 Why (is your web page) slow
 Set of rules

Firebug extension


Yslow: Performance View


Yslow: Stats


Yslow: Components


Yslow: Tools
 Print View
 JSLint


Make Fewer HTTP Requests
 Combined files
▹ CSS
▹ JavaScript

CSS sprites


Combined files
 Release process
 CSS
▹ Consider URLs

JavaScript
▹ Minify
▹ Obfuscate


CSS Sprites
 Elements with fixed size
 Background image

Disable repeat

Negative positions


CSS Icons
 Raster of icons
 No repeat

Fixed size
<div> or <span>


CSS Backgrounds
 Gradient
 Repeat in one
direction


Minify Javascript
 Most JS libraries provide a minified version
 YUI Compressor: http://developer.yahoo.com/
yui/compressor/
▹ JS and CSS

Packer
▹ Webpage, .Net, Perl, PHP
▹ http://dean.edwards.name/packer/


#2 Use A CDN
 Content Delivery Network
▹ Akamai Technologies
▹ Mirror Image Internet
▹ Limelight Networks

Bring the content to your users
▹ Geographic distance
▹ Physics is still here
 Only for large sites
 Dynamic content is complex

Headers
 Expires
 Cache-Control
▹ Session-Management

304 Not Modified


Expires
 Apache mod_expire

<IfModule mod_expires.c>
ExpiresDefault quot;access plus 1 monthquot;
ExpiresActive on
</IfModule>


Cache-Control
 nocache
▹ no caching
▹ default for sessions

private
▹ cacheable in browser cache

public
▹ cacheable in browser cache and proxies


304 Not Modified
 Send Etag and Modfication date
▹ Etag: quot;some hashquot;
▹ Last-Modified: Thu, 12 Sep 2008 11:00:00 GMT
 Request headers
▹ If-Modified-Since: Tue, 12 Sep 2008 11:00:00 GMT
▹ If-None-Match: quot;some hashquot;

Response headers
▹ HTTP/1.1 304 Not Modified

HTTPFox
 Firefox Extension
 Log of all HTTP requests

Not only displayed content


Gzip Components
 Gzip != Zip
▹ only compression
▹ no packaging
▹ tar.gz

Good browser support
▹ Accept-Encoding: gzip, deflate
▹ Content-Encoding: gzip


Gzip in Apache
 mod_gzip
 mod_deflate
▹ filter chain, works on dynamic content, too

▹ http://httpd.apache.org/docs/2.2/mod/mod_deflate.html


Gzip In PHP 5
<?php
ob_start('ob_gzhandler');
...


Gzip In PHP 5
<?php
if (function_exists('ob_gzhandler')) {
ob_start('ob_gzhandler');
}
...


Configure ETags
 Browser still asks webserver
 Server specific
▹ CDN
▹ Load balancer with multiple servers
 Apache
▹ FileETag none

IIS
▹ http://support.microsoft.com/?id=922733

Split requests across
domains
 HTTP 1.1 suggests 2 parallel requests per
domain
 Separate content by function
▹ www.domain.tld
▹ themes.domain.tld
▹ usercontent.domain.tld (security)

Optimisation tools change the option

Consider cookie domains

Reduce DNS Lookups
 DNS maps host names to ips
 Needs time
▹ 20-120 milliseconds

Cached in browser


Avoid Redirects
 Obviously additional requests
 Only cached with explicit headers
▹ depends on webserver configuration


http://www.domain.tld
▹ http://www.domain.tld/


Put Stylesheets at the Top
 Progressive display of the page
 Page appears to load faster

W3C specifications


Put Scripts at the Bottom
 Scripts block parallel downloads
▹ defer attribute in MSIE

onload() event
▹ used by most libraries


Problem: document.write()
▹ Counter
▹ Banners

Avoid CSS Expressions
 MSIE from version 5
▹ cross browser experience

JavaScript inside CSS

Evaluated
▹ page render
▹ resize
▹ scrolling
▹ mouse movements (hover)

JavaScript And CSS Files
 Do not embed JS/CSS in your pages
▹ No <script>...</script>
▹ No <style>...</style>

Separate caching headers

Revision parameter (style.css?rev=1234)
▹ Get parameter
▹ Unique URL for browser


Remove Duplicate Scripts
 Team size
 Standard scripts
▹ XMLRPC, JQuery, Prototype

Script module for your template system

 $templatesystem->addScript('foo.js');


Make Ajax Cacheable
 Often AJAX applications avoid caching
▹ http://some.domain.tld/ajax.file?t=randomvalue

A lot of requests

Use more static URLs


References
 Slides: http://www.abasketfulofpapayas.de/
 Yahoo Performance Team
▹ http://developer.yahoo.com/performance/
 JS minimize
▹ http://developer.yahoo.com/yui/compressor/
▹ http://dean.edwards.name/packer/
 Apache GZIP
▹ http://httpd.apache.org/docs/2.2/mod/mod_deflate.html
 No Etag in IIS
▹ http://support.microsoft.com/?id=922733

Optimizing Your Frontend Performance

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