steve souders [email protected] even faster websites disclaimer: this content does not necessarily...

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Steve Souders [email protected] http://stevesouders.com/docs/cbs-20090209.ppt Even Faster Websites Disclaimer: This content does not necessarily reflect the opinions of my

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Page 1: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Steve [email protected]

http://stevesouders.com/docs/cbs-20090209.ppt

Even Faster Websites

Disclaimer: This content does not necessarily reflect the opinions of my employer.

Page 2: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

17%

83%

iGoogle, primed cache

The Importance of Frontend Performance

9% 91%

iGoogle, empty cache

Page 3: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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%April 2008

Page 4: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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

Page 5: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

14 Rules1. Make fewer HTTP

requests2. Use a CDN3. Add an Expires header4. Gzip components5. Put stylesheets at the

top6. Put scripts at the

bottom7. Avoid CSS expressions8. Make JS and CSS

external9. Reduce DNS lookups10.Minify JS11.Avoid redirects12.Remove duplicate

scripts13.Configure ETags14.Make AJAX cacheable

Page 6: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

High Performance Web Sites

YSlow

Page 7: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

http://en.oreilly.com/velocity2009 June 22-24, 2009

Page 8: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect
Page 9: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Even Faster Websites

1. Split the initial payload2. Load scripts without blocking3. Don't scatter inline scripts4. Couple asynchronous scripts5. Split dominant domains6. Simplify CSS Selectors7. Use iframes sparingly8. Flush the document early

O'Reilly, Q2 2009

Page 10: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

AOLeBayFacebookMySpaceWikipediaYahoo!

Why focus on JavaScript?

YouTube

Page 11: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Scripts Block

<script src="A.js"> blocks parallel downloads and rendering

What's "Cuzillion"?

http://stevesouders.com/cuzillion/?ex=10008

Page 12: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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%

26% avg252K avg

Initial Payload and Execution

Page 13: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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?

Page 14: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

MSNScripts 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.com: Parallel Scripts

Page 15: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Advanced Script Loading

XHR Eval

XHR Injection

Script in Iframe

Script DOM Element

Script Defer

document.write Script Tag

Page 16: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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

Page 17: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

XHR Injectionvar 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 pagehttp://stevesouders.com/cuzillion/?ex=10015

Page 18: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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 pagewindow.frames[0].createNewDiv();

// access main page from iframeparent.document.createElement('div');

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

Page 19: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Script DOM Elementvar 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

Page 20: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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

Page 21: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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

parallelization only works in IE

parallel downloads for scripts, nothing else

all document.writes must be in same script block

http://stevesouders.com/cuzillion/?ex=10014

Page 22: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Browser Busy Indicators

Page 23: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Browser Busy Indicators

good to show busy indicators when the user needs feedback

bad when downloading in the background

Page 24: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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

immediatelyhttp://stevesouders.com/cuzillion/?ex=10019

Ensure/Avoid Ordered Execution

Page 25: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Summary of Traits

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

Page 26: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

and the winner is...XHR EvalXHR InjectionScript in iframeScript DOM ElementScript Defer

Script DOM ElementScript Defer

Script DOM Element

Script DOM Element (FF)Script Defer (IE)

XHR EvalXHR InjectionScript in iframeScript DOM Element (IE)

XHR InjectionXHR EvalScript DOM Element (IE)

Managed XHR InjectionManaged XHR EvalScript DOM Element

Managed XHR InjectionManaged XHR Eval

Script DOM Element (FF)Script Defer (IE)Managed XHR EvalManaged XHR Injection

Script DOM Element (FF)Script Defer (IE)Managed XHR EvalManaged XHR Injection

different domains same domains

no order

preserve order

no order

no busyshow busy

show busyno busy

preserve order

Page 27: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Load Scripts without Blocking

don't let scripts block other downloads

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

What about inline scripts?

Page 28: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Inline Scripts after Stylesheets Block Downloading

Firefox 3 and IE download stylesheets in parallel

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

http://stevesouders.com/cuzillion/?ex=10021

best to move inline scripts above stylesheets or below other resources

use Link, not @import

Page 29: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

eBayMSNMySpaceWikipedia

Examples of Scattered Scripts

Page 30: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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

Page 31: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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 13K+ tests, 9K+ unique testers, 50+ browsers

help out by running the test!

Page 32: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Measuring Performance

Episodes

dev box synthetic testing

bucket testing

real user data

Hammerhead

Page 33: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

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 dataload time measurementmodal cache clearing

combine with bandwidth throttler

Page 34: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

CNet Performance Analysis

cool– flushed document– HTTP/1.0 downgrade

opportunities– load oreo.moo.rb.combined.js async– split i.i.com.com across two domains– concatenate 10 scripts– sprite 25 CSS background images– 30 resources with short Expires– 62% (62K) of CSS not used

requests: 107load time: 3.7

secsxfer size: 436KYSlow: F (48)

Page 35: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

BNet Performance Analysis

cool– flushed document– @import stylesheets

opportunities– compress 235K (16 files)– sprite 57 CSS background images– concatenate 12 scripts, 6 stylesheets– optimize images (30K, 16%)– 106 resources with short Expires– 60% (29K) of CSS not used– remove ETags

requests: 149load time: 5.9

secsxfer size: 759KYSlow: F (26)

Page 36: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

cool– flushed document

opportunities– compress 151K (11 files)– move inline script above stylesheets– concatenate 16 scripts– sprite 26 CSS background images– optimize images (104K, 28%)– move www.cbssports.com images to a CDN– split images.cbssports.com across two domains– almost all resources have a short Expires– 49% (24K) of CSS not used– minify 63K (8 scripts)– remove ETags

requests: 99load time: 8.2

secsxfer size: 689KYSlow: F (31)

CBSSports Performance Analysis

Page 37: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Takeaways

focus on the frontend

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

this year's focus: JavaScriptSplit the Initial PayloadLoad Scripts without BlockingDon't Scatter Inline Scripts

speed matters

Page 38: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Impact on Revenue

Google:

Yahoo:

Amazon:

1 http://home.blarg.net/~glinden/StanfordDataMining.2006-11-29.ppt2 http://www.slideshare.net/stoyan/yslow-20-presentation

+500 ms -20% traffic1

+400 ms -5-9% full-page traffic2

+100 ms -1% sales1

Page 39: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Cost Savings

hardware – reduced load

bandwidth – reduced response size

http://billwscott.com/share/presentations/2008/stanford/HPWP-RealWorld.pdf

Page 40: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

if you wantbetter user experiencemore revenuereduced operating expenses

the strategy is clear

Even Faster Websites

Page 41: Steve Souders souders@google.com  Even Faster Websites Disclaimer: This content does not necessarily reflect

Steve [email protected]

http://stevesouders.com/docs/cbs-20090209.ppt