web performance optimization

Web Performance Optimization

2010 © Pavel Paulau

Getting started

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• Look into web front-ends performance

• Learn how to- Estimate and track web performance- Analyze and diagnose page bottlenecks- Make website faster easily without code modification and eye candy losses

• Forget for a hour about load, transactions and servers

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End user experienceEnd user experience1

Automated web performance testingAutomated web performance testing2

In-depth performance analysisIn-depth performance analysis3

Effective content delivery and transformationEffective content delivery and transformation4

Optimization examplesOptimization examples5

ConclusionConclusion6

Performance aspects

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• AvailabilityThe amount of time an application is available to the

end user.

• Response timeThe amount of time it takes for the application to respond

to a user request.

• ThroughputThe rate at which application-oriented events occur.

• UtilizationThe percentage of the theoretical capacity of a

resource that is being used.

Behind the scene

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• Just one user’s click lead to- Tens of HTTP requests- Hundreds of XHR calls- Kilobytes of network traffic- Multiple CPU calls- Expensive IO operations

• However, the end user doesn’t know anything about HTTP, web technologies, browsers and servers

• The only thing the user experiences is a page load time

Challenges

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• Traditional performance testing techniques do not reflect real browser behavior

• Dependence on connection quality

• Multiple browsers and versions of browsers

• Lots of components and pages

• Third-party components

• A false view of the performance bottlenecks

Browsers multiplicity

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Firefox 3.x30.5

Opera 101.2

Chrome 57.6

IE 68.1Chrome 6

2.7

IE 829.3

Safari 52.6

IE 713.9

Safari 41.1

Browser Connections per Hostname* II Scripts Script* II Scripts Stylesheet* II Scripts Image* Async. Scripts* Cache Redirects*Chrome 5 6 Yes Yes Yes No YesChrome 6 6 Yes Yes Yes No YesFirefox 3.x 6 Yes Yes Yes Yes YesIE 6 2 No No No No NoIE 7 2 No No No No NoIE 8 6 Yes Yes No No NoOpera 10 8 No No No No NoSafari 4 6 Yes Yes Yes No NoSafari 5 6 Yes Yes Yes No Yes

* browserscope.org

Different browsers offer different performance

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Source: Gomez Real-User Monitoring

> Real users around the world> Broadband

> 466M pages over 30 days> 200+ sites

Response time components

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Server side Content delivery Rendering

Outside the application -still part of our responsibility

Critical forWeb 2.0

application

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

Web performance anatomy

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ServerBrowser

Latency

HTTP

Cache

ParsingLayoutingRendering

Ads, widgets, analytics

ImagesCSSJavaScriptFlash

DNS Server

3rd-partyservers

Internet

AJAX/XHRIE

FirefoxChrome

SafariOpera

Performance impact

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• E-commerce applications- People stay on website longer and view more pages

- People perceive business to be more trustworthy

- Significantly decreased visitor frustration levels

- Google uses site speed in web search ranking

• Enterprise applications- Faster responses keep users more attentive and

concentrated

- Some business processes require extremely fast interactions

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Performance metrics

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There are two basic approaches to performance estimation• Time-driven testing – measuring absolute load time

- Time to first byte

- Time to first impression

- onLoad time

- Fully loaded time

• Rank-driven testing – based on best practices- Yahoo! YSlow grades

- Google Page Speed scores

- dynaTrace AJAX edition ranks

Test automation framework

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Analyst workstation Test environment LAMP (WAMP) Server

Show Slow

WebPagetest

URL Blast

Selenium Remote-Control

Test Controller(Java, C#, Python,Ruby, Perl, PHP)

Advantages

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• Open source solution> Free and flexible

• Websites testing with real browsers, not via HTTP requests

> Parsing and rendering aren’t ignored

• End-to-end process> Benchmark → Analysis → Optimization

• Scripting using the most popular languages> Java, C#, Python, Ruby, PHP, Perl.

Features. Results storage and visualization

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• Test results stored in MySQL database. Reliable and accessible approach

• “Measurements over time” feature provides the continuous control support

• Screen shots, waterfall views, visual comparison, video capture, content and domain breakdowns… not a full list of analytic solutions

Features. WAN emulation

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• Using Dummynet it’s possible to define the following connection options:

- Bandwidth download speed- Bandwidth upload speed- Network latency- Packet loss

• That’s an extremely important feature for worldwide applications without CDN

Features. Optimization checklist

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Available tools

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• Free and open source tools available for almost any browser:- Firebug with add-ons (Firefox)

- dynaTrace Ajax Edition (IE)

- Speed Tracer (Chrome)

- Web Inspector/Developer Tools (Safari/Chrome)

- HttpWatch (IE/Firefox)

- Dragonfly (Opera)

• These tools vary in functionality, flexibility and advantages, but together provide amazing capabilities

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It’s possible just to grade web pages total performance with any general rating system

or KPI’s.

Performance Ranking

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Sometimes it is not unlikely to notice a problem at a glance – just with HTTP waterfall charts. Blocking issues, non-existent elements, too long requests could be found within a minute.

HTTP waterfall charts

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Understanding of what is really going on inside of browser is a key point of page speed

analysis.

Timeline analysis

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When JavaScript becomes a trouble it’s extremely easy to analyze code execution and find the most

expensive call

JavaScript Profiling

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Not only JS-scripts but style spreadsheets lead to performance issues.Additional analysis features provide an ability to controls the effectiveness of CSS usage

CSS Usage Analysis

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The most delicious feature of these tools is a strong possibility to get an instantaneous advice

based on diverse best practices

Optimization advices

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• Eliminate wasteful work

• Identify the action that's consuming most of user response time.

• Make the application do that action less often.

• Make the application do that action faster.

The fastest way to do something is don’t do it

Common optimization principles

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Google, Yahoo! and dynaTrace specialists provide and constantly update best practices on

Cache optimization

Round-trip times minimization

Components size minimization

Parsing and rendering optimization

Available best practices

Cache optimization

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• A first-time visit to a page may require several HTTP requests to load all the components.

• By using Expires or Cache-Control headers these components become cacheable, which avoids unnecessary HTTP requests on subsequent page views.

• Expires headers are most often associated with images, but they can and should be used on all page components including scripts, stylesheets and Flash.


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• Decreasing the number of components on a page reduces the

number of HTTP requests and network packets required to

render the page, resulting in faster page loads.

• Common way to reduce the number of

components includes- Combine multiple scripts into one script

- Combine multiple CSS files into single stylesheet

- Use CSS Sprites and image maps


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• Inserting a redirect between the user and the final HTML document delays everything on the page since nothing on the page can be rendered and no components can be downloaded until the HTML document arrives.

• Reference to missing resources is a time wasting process

XHR calls minimization

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• JavaScript and XmlHttpRequests are the basis for what in general is called AJAX. Frameworks like jQuery make it very easy to make AJAX calls in order to retrieve additional content from the server.

• When the user navigates to the next page we request the next page via an AJAX call and refresh the DOM. This avoids a full round-trip and avoids the browser reloading the whole page.

• A mistake that is often made is that too much information is fetched dynamically with too many calls.

Component size minimization

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• Most modern browsers support data compression for HTML, CSS, and JavaScript files. This allows content to be sent over the network in more compact form and can result in a dramatic reduction in download time.

• Gzip is the most popular and effective compression method currently available and generally reduces the response size by about 70%.

Component size minimization

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• Minification removes unnecessary characters from a file to reduce its size, thereby improving load times.

• When a file is minified, comments and unneeded white space characters (spaces, newlines, and tabs) are removed. This improves response time since the size of the download files is reduced.

• Properly formatting and compressing images can save many bytes of data.

Rendering optimization

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• JavaScript scripts block parallel downloads - to help the page load faster, move scripts to the bottom of the page if they are deferrable.

• Moving stylesheets to the document head element helps pages appear to load quicker since this allows pages to render progressively.

• Specifying a width and height for all images allows for faster rendering by eliminating the need for unnecessary reflows and repaints.

Effective DOM manipulation

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• Many JavaScript libraries provide nice visual effects, e.g: dynamic popup menus, accordion effects, etc.

• Where most of these frameworks do a good job on sample web sites, some of them do not perform well on real life pages with large DOMs.

• It is important to analyze the impact of visual effects on the browser’s CPU, the rendering engine and the overall web site performance.

3-rd party components

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• You can't control it all

• Speed up what you can

Ensure that things you have control over are lightening fast

• Defer everything you can't control

Make sure it’s the last thing that is called on the page before it's done loading

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Sotheby’s landing page

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• Page load time (IE7, 1024/512 Kbps, 50 ms RTT)• 15.5 seconds (first view)• 7.5 seconds (repeat view)

• Google Page Speed score• 67 (D)

• Yahoo! YSlow grade• 63 (D)

• dynaTrace AJAX edition rank• 73 (C)

Optimization list

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CSS merging eliminates 33 HTTP requests.

JS merging eliminates 16 HTTP requests.

CSS, JS and HTML minimization saves about 160 kilobytes of network traffic.

Images optimization reduce the page size by about 130 kilobytes.

GZip compression removes 420 kilobytes of unnecessary network traffic.

Cache tweaks (Expire headers and ETag optimization) to make repeat load faster.

Automatic adjustments with Apache mod_pagespeed.

Page resources

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Before

After

Performance metrics

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15.5 s

5.5 s

First View7.5 s

2.5 s

Repeat View

Page load time – 3x faster

Optimization ranks

67 (D)

91 (A)

Page Speed

63 (D)

90 (A)

YSlow

73 (C)

96 (A)

dynaTrace

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Resume

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• Websites performance matters

• Traditional performance testing techniques cover only smallest part of the end user experience

• There are methods and tools to test, analyze and optimize websites speed

• These methods don’t contradict common performance testing approaches but complement them

Do not ignore front-ends!

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Books- High Performance Web Sites

- Even Faster Web Sites

- Website Optimization

- Complete Web Monitoring

- High Performance JavaScript

Web- Google Web Performance Best Practices

- Yahoo! Best Practices for Speeding Up Your Web Site

- DynaTrace Best Practices on Web Site Performance Optimization

Best practices

http://code.google.com/intl/ru-RU/speed/page-speed/docs/rules_intro.html

http://developer.yahoo.com/performance/rules.html





https://community.dynatrace.com/community/display/PUB/Best+Practices+on+Web+Site+Performance+Optimization

https://community.dynatrace.com/community/display/PUB/Best+Practices+on+Web+Site+Performance+Optimization

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Tools

Google Page Speed Tools Familyhttp://code.google.com/speed/page-speed/

dynaTrace AJAX Editionhttp://ajax.dynatrace.com/ajax/en/

Yahoo! YSlowhttp://developer.yahoo.com/yslow/

WebPagetesthttp://www.webpagetest.org/

Show Slowhttp://www.showslow.com/

Let's Make the Web Fasterhttp://code.google.com/intl/en-EN/speed/tools.html

http://code.google.com/speed/page-speed/

http://ajax.dynatrace.com/ajax/en/

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

http://www.webpagetest.org/

http://www.showslow.com/

http://code.google.com/intl/en-EN/speed/tools.html

web performance optimization

Technology

track web performance

eye candy losses

code modification

page bottlenecks