What is performance?

• Performance is how fast your site works
• NOT how many users it can serve (Scalability)
• NOT how often it's down (Reliability)

Why do we need to care?

• User experience
• Money!!!
  • +100ms → -1% sales (Amazon) *
  • +400ms → -5-9% full-page traffic (Yahoo! Autos front page) **
  • +500ms → -20% searches (Google) ***
  * Make Data Useful, Greg Linden at Stanford Data Mining class, fall 2006
  ** YSlow 2.0 early preview in China, Stoyan Stefanov, December 6^th, 2008
  *** Scaling Google for Every User, Marissa Mayer at Google Seattle Conference on Scalability 2007 (video)

Backend & Frontend

• Browser (front-end)
• Web/app server
• Relational database

DataBase performance

• use INDEXES = use "EXPLAIN" to understand your situation *
• Configure query cache **
• Use correct datatypes to put as much stuff into memory as possible ***
• Read documentation for your RDBMS

Compile

Compiled code is faster then interpreted

• ASP.NET, Java, Python compile into bytecode
• APC for PHP *
• mod_perl
• What's for Ruby? JRuby?

Cache & static files

• Cache results
  • Shared memory (APC and EAccelerator for PHP)
  • memcached
• Reverse proxies (Squid)
• CDNs (Akamai, Limelight)
• mystaticfiles.net with lightweight servers (nginx, lighttpd)

Front-end: Start Here!

1995 - 2008

* Average Web Page Size Triples Since 2003, as of end of 2007 (via Nicole Sullivan)

Front-end: Start Here!

Jun 2006 - Jan 2008

* Average Web Page Size Triples Since 2003, as of end of 2007 (via Nicole Sullivan)

Amazon Waterfall!

• Total Requests: 88
• Total Time: 6.344 seconds
• Back-end Time: 0.968 seconds = just 15%

CNN Waterfall!

• Total Requests: 174
• Total Time: 4.406 seconds
• Back-end Time: 0.171 seconds = less then 4%

What's going on? Analytical tools

• YSlow for Firebug
• Waterfalls:
  • Firebug's Net panel (Firefox)
  • WebPageTest.org and AOL Page Test (IE, connection summary, scriptable)
  • Fiddler (WinINET, works with Firefox as proxy)
  • HttpWatch ($$$, Firefox and IE, shows cache hits)
  • Keynote's KITE, Gomez Instant Test Pro (geo, enterprise, limited free versions)

What's going on? Monitoring tools

• Enterprise level
  • Gomez
  • Keynote
• Open Source
  • ShowSlow - YSlow monitoring (shameless plug)

JS, CSS, Images

Content Compressors

• JSMin (JS), YUI Compressor (JS and CSS)
• SmushIt.com, OptiPNG for images
• gzip, mod_deflate (backend)

CSS Sprites

• Spritegen by Project Fondue

More info

• TechPresentations.org/Performance
• Follow the rules (34)

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