Web Performance Optimization Just one second please !

Maxime Lemaitre

• Introduction

• Goals & Objectives

• Why performance matters ?

• Web application delivery chain

• Some rules & Some tools

• Next Steps

2

Agenda

• Evangelize performance and explain why it is important – Have a performance culture !

– Have a performance plan !

• Do performance tests, setup production metrics & KPIs, do monitoring and reports

• And of course, increase responsiveness of your website !

3

Goals & Objectives

• We won’t talk (today) about

– Load Testing

– How to write efficient data acces queries

– Which is the fastest between C#, Java or Php ?

– ….

4

Web performance matters ? short history : from a tech challenge to a differentiator

• First decade of the web's existence (1993 – 2003).

– Performance focus on :

• Optimize website code (simple scripts)

• Improve data access (use indexes, fewer queries, …)

• Reduce packet loss and retransmission

• Pushing hardware limitations (CPU, Memory, IO…)

Not focused on browser display speed

• An emerging industry (2004-2009)

– Steve Souders (Yahoo), pioneer in « web performance optimization »

• 85% of the time that it takes to download and view a website is controlled by the front-end structure

• 10 predictions (fast by default, Visibility into the browser, monitoring, mobile, … => a differientator)

– Velocity 2009 Conference is a key event in web performance

• Many case studies from Microsoft, AOL, Amazon, ShopZilla , …

• Not only for techs but also other parts of the organization (management, marketing, sales, …)

• Last years (2010 – Now)

– Google : « we’ve decided to take site speed into account in our search rankings »

– For an ecommerce website, it’s been proven that speed = money

– Trend : make the web faster because web pages are bigger and more complex than ever

Bing : page that was 2 seconds slower resulted in a 4.3% drop in revenue/user

Yahoo : 400 milliseconds slowdown resulted in a 5-9% drop in full-page traffic

Google : 400 millisecond delay caused a 0.59% drop in searches/user

Even after the delay was removed, these users still had -0.21% fewer searches

slower user experience affects long term behavior

AOL : page views drop off as page load times increase

Mozilla : Shaving 2.2 seconds off their home page increased downloads by 15.4%

ShopZilla : 5 second speed up

• 25% increase in page views

• 7-12% increase in revenue

• 50% reduction in hardware

Amazon : Every 100ms delay costs 1% of sales

5

Web performance matters ? case studies in web industry

6

Why performance matters ? for customers (source : Velocity Conf, Aberdeen, Gomez, Akamai)

Is Web Performance important for your company ?

• Are you in a competitive industry ?

• Do you sell something ?

• Does another website sell basically the « same thing »

• Is is important to attract new users ?

• Is SEO important for you ?

• Does you marketing team wants to show everything on your homepage ?

• ….

• Better user experience

– Customers will be happier and will tell others how good we are

– Keep them more focused on our content, rather than waiting for scripts/images

• Improve SEO

– One of the 200 signals used in Google Rankings

• Mobile performance : a new challenge

– Tablets/Smartphones are slower than desktops

– Much more limits and latency

• Improve conversion rate

– every second win, will boost customer confidence and trust in your site

• Reduce costs

– Bandwidth

– Less Hardware/Servers

• Better Scalability

7

Why performance matters ? for techs & devs

• Final page speed is a depending on

– User computer and browser

– User current activity

– User network connection/ISP

– Internet Backbone

– Web Hosting location

– HTML (JS, CSS, Images, ..)

– Third-Party libraries / Ads / Analytics

– CDN

– Firewall/Load balancer

– Web Page / server code

– Frontend servers / Web Farms

– API/WebServices Calls

– Middle Tier / Backend servers

– Database

– …

8

Web Application Delivery Chain performance at the bottom line

Do not trust that every user have a

Core i5 CPU with 8 Go Ram on

Windows 7 on a 100 Mbits/s

connection ! It’s false !

Try to test performance on slowest

computers and slowest bandwidth

80-90% of the end-user response time is spent on the frontend !

9

Web Performance where to start ?

“We should forget about small efficiencies, say about 97% of the time: premature optimization is

the root of all evil” Donald Knuth

Never automatically apply tips, best practices & improvements without checking before/after the changes.

=> Profiling and Micro-Benchmark

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Important Note before going deeper

• Yslow & PageSpeed – Proven front-end best practices & recommandations

– Very popular & easy to install (browser extension or online service)

– Current : Yslow (23 best practices) & PageSpeed (31 rules)

• But … – does not look at our Infrastructure, Application Performance, CDN, DB Queries,

datacenter distribution, load balancing, …

– does not include the actual speed of the tested page !

– Lower scores/grades can load faster than Higher scores

11

Web Performance auditors Google PageSpeed & YSlow

Html Parsing Pipeline how page loads

• Loading a page is not as simple as dowloading a single file

– Involve dynamic ressources

– Cascading stylesheet

– Javascripts

• Common performance issue : Because JavaScript code can alter the content and layout of a web page, the browser delays rendering any content that follows a script tag until that script has been downloaded, parsed and executed.

Many browsers block the downloading of resources referenced in the document after scripts until those scripts are downloaded and executed

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Round-trip time (RTT) is the time it takes for a client to send a request and the server to send a response over the network, not including the time required for data transfer.

• Minimize redirects

• Use HTTP Cache Headers

• Avoid bad/duplicated/useless requests

• Combine external JavaScript & Css

• Combine images using CSS sprites

• Optimize the order of styles and scripts

• Prefer asynchronous resources (Async or Deferred JS)

• Parallelize downloads across hostnames

• …

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Golden Rule #1 minimize round-trip times

Downloading 50 B always have a cost !

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Less than 6 connections per hostname Limit number of requests

Amount of data sent in each server response can add significant latency, especially in areas where bandwidth is constrained

• Enable Gzip compression

• Limit HTTP Headers (Uncompressed)

• Remove unused CSS/JS/comments

• Avoid inline/embedded styles and scripts

• Minify CSS & JavaScript

• Minify HTML

• Optimize, Optimize, Optimize images

• Serve scaled images

• …

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Golden Rule #2 Minimize Request Overhead & payload size

Web images take up the majority of the download time in most web pages

• Choose an appropriate file format (JPG, PNG, GIF)

– For JPG, use progressive image (demo)

• Optimize image size

– Crop whitespace, Remove useless data (color palette, EXIFF, ..)

– Apply a Lossless compressor (OptiPNG or PNGOUT)

• Try to apply width and height for each <img> tag

– Avoid unnecessary repaints and reflows during rendering

– But do not use it to scale images : server already scaled images

• Use Sprites (see )

– reduced the number of HTTP requests and avoided any potential delay

• Use Data-URI

– inline the content of the URI you would normally point to

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Images Optimizations Web images take up the majority of the download time in most web pages

Once resources have been downloaded to the client, the browser still needs to load, interpret, and render HTML, CSS, and JavaScript code.

• Limit Number of DOM elements

• Defer loading of JavaScript and Third party components

• Avoid DOM alterations

• Styles at top, Scripts at bottom

• Use efficient CSS selectors & Avoid CSS expressions

• Specify image dimensions

• Specify a character set

• Check Javascript and especially Jquery performance

• …

Google SpeedTracer could help you (home)

low level instrumentation points inside Chrome 17

Golden Rule #3 Optimize Browser rendering

• Styles are downloaded and applied when rendering

Browsers block rendering a web page until all external stylesheets have been downloaded

- Put styles in head allow the browser to progressively render the page

- Put styles in body can cause repaints & reflows (demo)

• Scripts are downloaded, parsed and executed

The page has to wait for the script blocks to be fully downloaded, parsed and executed before being able to parse and render any following HTML

– Block the rendering of any following HTML

– Block the downloading of resources referenced in the document after the script

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Quick Focus : Styles & Scripts Why is it so important to optimize styles & scripts?

What is the page speed (with/without Cache) for this ridicoulous page ?

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Scripts Stop paying the Script tax

• First View

• Repeat View

• Repeat View (on my laptop in power saving mode)

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Scripts Stop paying the Script tax²

Even from cache (no download), it takes a few ms to parse & exec Scripts.

Not so fast …

Easy to write JavaScript …

…and easy to write really really bad JavaScript and slow down page load

• Minimal recommandations

– Always use the latest version of Jquery (test) jQuery team is always looking to bring improvements

– Use appropriate selections (test) Many ways to select an element, but they don’t have the same performance

Id < Tag < Class

– Do not repeat selectors & abuse chain Cache results & object

– Use for instead of foreach (test) Native JavaScript functions is always faster

– Do use Jquery … if possible (test) Native JavaScript functions is always faster²

• Continue Reading here

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Jquery Performance with great power comes great responsibility (Spiderman)

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How to mesure/improve performance ? hopefully there are many tools !

• Sql Profiler

• Graphite

• Web Developpers Tools

• WebPageTest.org

• PhantomJS

• Selenium Web Driver

• Har Viewer

• Google Page Speed

• Yslow

• dotTrace

• Pingdom tools

• Fiddler

• jsPerf

• MVC MiniProfiler

• dynaTrace

• Google Analytics

• IIS & Apache Logs

• Performance coutners

• Visual Studio Web Perf

• Gtmetrix

• Micro Benchmark

• Google Site Speed

• Centreon

• New Relic

• Node.js

• DB Provider Client Statistics

• SpeedTrace

• Headless Browsers

• Boomerang.js

• MVC Bundles

• Optipng

• Glimpse

• SpriteMe

• Firebug

• Your own tool here!

• Learn how to improve Web performance

• Investigate available performance tools

– Dev customs tools if necessary

• Automate performance testing

• …

It’s only the beginning !

PS : And of course, check Performance of your Web Site

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Next Steps

• https://developers.google.com/speed/

• http://developer.yahoo.com/performance/

• http://www.webpagetest.org/

• http://ie.microsoft.com/testdrive/HTML5/DOMContentLoaded/Default.html

• http://www.softwareishard.com/har/viewer/ (HAR file viewer)

• https://github.com/blog/1252-how-we-keep-github-fast (github performance)

• http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#parsing (Parsing HTML Documents)

• http://www.stevesouders.com/blog/2010/05/07/wpo-web-performance-optimization/ (must read)

• http://dmix.ca/2010/01/the-marketing-of-sports-betting-sites/ (betting industry)

• http://sixrevisions.com/tools/8-excellent-tools-for-optimizing-your-images/

• http://www.browserscope.org

• http://browserdiet.com/

• http://gtmetrix.com/

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Appendices

Yslow Best Practices

Add Expires headers

Avoid AlphaImageLoader filter

Avoid CSS expressions

Avoid empty src or href

Avoid HTTP 404 (Not Found) error

Avoid URL redirects

Compress components with gzip

Configure entity tags (ETags)

Do not scale images in HTML

Make AJAX cacheable

Make favicon small and cacheable

Make fewer HTTP requests

Make JavaScript and CSS external

Minify JavaScript and CSS

Put CSS at the top

Put JavaScript at bottom

Reduce cookie size

Reduce DNS lookups

Reduce the number of DOM elements

Remove duplicate JavaScript and CSS

Use a Content Delivery Network (CDN)

Use cookie-free domains

Use GET for AJAX requests

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Avoid a character set in the meta tag

Avoid bad requests

Avoid CSS @import

Avoid CSS expressions (deprecated)

Avoid document.write

Avoid Flash on mobile webpages

Avoid landing page redirects

Combine external CSS

Combine external JavaScript

Combine images using CSS sprites

Defer loading of JavaScript

Defer parsing of JavaScript

Enable gzip compression

Enable Keep-Alive

Improve server response time

Inline small CSS

Inline small JavaScript

Leverage browser caching

Leverage proxy caching (deprecated)

Make landing page redirects cacheable

Minify CSS

Minify HTML

Minify JavaScript

Minimize cookie size (deprecated)

Minimize DNS lookups

Minimize redirects

Minimize request size

Optimize images

Optimize the order of styles and scripts

Parallelize downloads across hostnames

Prefer asynchronous resources

Put CSS in the document head

Remove query strings from static resources

Remove unused CSS

Serve resources from a consistent URL

Serve scaled images

Serve static content from a cookieless domain

Specify a cache validator

Specify a character set early

Specify a Vary: Accept-Encoding header

Specify a viewport for mobile browsers

Specify image dimensions

Use an application cache

Use efficient CSS selectors

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PageSpeed Rules