Widget Summit 2008

Steve Souders [email_address] http://stevesouders.com/docs/widget-summit-2008.ppt High Performance Widgets Disclaimer: This content does not necessarily reflect the opinions of my employer.

The Importance of Frontend Performance 17% 83% iGoogle, primed cache 9% 91% iGoogle, empty cache

Time Spent on the Frontend April 2008 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%

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

14 Rules

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

High Performance Web Sites YSlow

http://conferences.oreilly.com/velocity/

June 22-24, 2009

High Performance Web Sites, Vol 2

Split the initial payload

Load scripts without blocking

Don't scatter inline scripts

Split dominant domains

Make static content cookie-free

Reduce cookie weight

Minify CSS

Optimize images

Use iframes sparingly

To www or not to www

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

Scripts Block <script src="A.js"> blocks parallel downloads and rendering What's "Cuzillion"? http://stevesouders.com/cuzillion/?ex=10008

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%

Split the initial payload split your JavaScript between what's needed to render the page and everything else load "everything else" after the page is rendered separate manually (Firebug); tools needed to automate this (Doloto from Microsoft) load scripts without blocking – how?

MSN.com: Parallel Scripts 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) MSN

Advanced Script Loading XHR Eval XHR Injection Script in Iframe Script DOM Element Script Defer document.write Script Tag

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

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

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');

http://stevesouders.com/cuzillion/?ex=10012

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

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 http://stevesouders.com/cuzillion/?ex=10013

document.write Script Tag document.write ("<scr" + "ipt type='text/javascript' src='A.js'>" + "</scr" + "ipt>"); 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

Browser Busy Indicators

Browser Busy Indicators good to show busy indicators when the user needs feedback bad when downloading in the background

Ensure/Avoid Ordered Execution

Ensure scripts execute in order:

necessary when scripts have dependencies

IE: http://stevesouders.com/cuzillion/?ex=10017

FF: http://stevesouders.com/cuzillion/?ex=10018

Avoid scripts executing in order:

faster – first script back is executed immediately

Summary of Traits * Only other document.write scripts are downloaded in parallel (in the same script block).

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

Load Scripts without Blocking

don't let scripts block other downloads

you can still control execution order, busy indicators, and onload event

Inline Scripts Block

long executing inline scripts block rendering and downloads

workarounds:

initiate execution with setTimeout (>250 for FF, nglayout.initialpaint.delay )

move JavaScript to external script with advanced downloading techniques

use Defer attribute (IE only)

Inline Scripts after Stylesheets Block Downloading

Firefox 3 and IE download stylesheets in parallel

...unless the stylesheet is followed by an inline script

best to move inline scripts above stylesheets or below other resources

use Link, not @import

Examples of Scattered Scripts eBay MSN MySpace Wikipedia

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

Get Satisfaction Widget

<div id="gsfn_content">Loading...</div>

<script _ src="http://getsatisfaction.com/oreilly/widgets/javascripts/5977e91/widgets.js" type="text/javascript"></script>

<script _ src="http://getsatisfaction.com/oreilly/topics.widget?callback=gsfnTopicsCallback&length=120&limit=5&sort=recently_active" type="text/javascript"></script>

...

function gsfn_populate(id, template) {

document.getElementById(id).innerHTML = template;

}

good

small

improve

add future Expires header – widgets.js, favicon.gif (not topics.widget)

gzip – wigets.js, topics.widget

minify widgets.js

remove ETags

use only one: getsatisfaction.com or www.getsatisfaction.com

load scripts async

3 requests 8K xfer size 8K JS (uncompr)

Google Calendar Widget

<iframe _

src="//www.google.com/calendar/embed

?mode=AGENDA

&height=600

&wkst=1

&bgcolor=%23FFFFFF

&src=v9ke3029e8k53qjtbf506jumu8ktapjh%40import.calendar.google.com

&color=%235A6986

&ctz=America%2FLos_Angeles"

style=" border-width:0 " width="800" height="600" frameborder="0" scrolling="no">

</iframe>

good

gzip turned on

no ETags

future Expires headers

improve

big! 135K JS, 18K CSS (uncompressed)

set iframe SRC dynamically

44% of JS unused

sprite 6 images into 1

/feeds/ is slow (only 2K, but longer than 133K JS)

10 requests 65K xfer size 135K JS (uncompr)

Google Friend Connect Widget

<div id="div-08054659623916314855-members"></div>

<script type="text/javascript">

var skin = {};

skin['HEIGHT'] = '150';

skin['HEADER_FOOTER_BG_COLOR'] = '#BFEECC';

skin['MEMBERS_LIST_BG_COLOR'] = '#D9FFE4';

skin['MEMBERS_LIST_FRIEND_LINK_COLOR'] = '#339966';

skin['MEMBERS_LIST_HEADER_FONT_COLOR'] = '#339966';

skin['INVITE_LINK_COLOR'] = '#339966';

google.friendconnect.container.renderMembersGadget( { id: 'div-08054659623916314855-members', site: '08054659623916314855' }, skin);

</script>

39 requests 188K xfer size 471K JS (uncompr) (3 widgets)

good

gzip turned on

no ETags

future Expires headers

improve

big! (really 3 widgets)

3 redirects – max-age=0

74% of JS unused

22 requests expire in 24 hours

173K of images – lossless compression cuts 87%

4 text/html responses not gzipped (total 19K)

6 CSS expressions

3 duplicate scripts – iframes

39 requests 188K xfer size 471K JS (uncompr) (3 widgets)

MyBlogLog Widget

var mbl_widget = '';

mbl_widget += '';

mbl_widget += ' <style>';

mbl_widget += ' a.mbl_widget {…}';

mbl_widget += ' a.mbl_widget_u {…}';

mbl_widget += ' a.mbl_widget_a {…}';

mbl_widget += '';

[321 lines later...]

mbl_widget += ' </div>';

mbl_widget += ' </div>';

mbl_widget += '';

document.write(mbl_widget);

good

sprite (v3_1_default_black.gif)

domain sharding

images optimized

improve

add future Expires (nopic_48.gif, close12_1.gif)

5 DNS lookups

avoid document.write

80% of JS unused

load script asynchronously

js 14 requests 60K xfer size 62K JS (uncompr)

Plaxo Widget

<div id="plaxo-pulse-widget"></div>

<script _ src="http://pulse.plaxo.com/pulse/widget/get?authTicket=265...4%3D&type=frame&version=2&height=480&width=125"></script>

iframe is appended to div

good

10 day future Expires

gzip enabled

domain sharding (Flickr)

backend stitching

improve

/badge is slow – start with previous request

do away with iframe altogether – one script

load script asynchronously – set size of div

4 images could be sprited into 1

js 14 requests 41K xfer size 2K JS (uncompr)

Announcement 1: 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 ~3K tests, ~2K unique testers, ~120 browsers

help out by running the test!

Measuring Performance

Episodes

dev box synthetic testing bucket testing real user data Hammerhead

Announcement 2: Hammerhead "moving 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

Takeaways

focus on the frontend

run YSlow: http://developer.yahoo.com/yslow

this year's focus: JavaScript

Split the Initial Payload

Load Scripts without Blocking

Don't Scatter Inline Scripts

speed matters

life's too short, write fast code

Steve Souders [email_address] http://stevesouders.com/docs/widget-summit-2008.ppt

Widget Summit 2008

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