Web Performance Bootcamp 2014

Web Performance Boot Camp
2014
Daniel Austin
Interstellar Travel, Inc.
HTML5 DevConf
May 21, 2014
V 0.9

Overture: Goals of the Class
• Provide a basic understanding of Web performance for
Architects, Developers, Designers, and Engineers
• Empower YOU to identify and resolve performance
problems and make your pages and applications faster!!!
• Demonstrate and explain how to use common tools and
techniques used in our industry to solve performance
problems

Self-Serving Promotion!
Available October 25, 2014
You can pre-order it on
Amazon now!
‘Rough Cuts’ preview
scheduled for June 2014.

Scope of Web Performance
Anything that uses HTTP
Always From the End User’s Point of View
Web Request/Response Only!

Current State of the Art
• Web performance is both an Art and a Science (but it’s not yet
Engineering)
• Multiple tools and methodologies, large ad hoc, contend in the
marketplace (but little of it is well-thought out or based on
scientific reasoning).
• Things are getting better – W3C involvement and competitive
pressures, as well as better infrastructure and the influx of new
users in Asia is driving more attention to performance. There’s
hope.

Reading List
• Performance by Design - Daniel A. Menasce (Safari)
• The Practical Performance Analyst - Neil J. Gunther
• Elements of Networking Style - M.A. Padlipsky
• High Performance Web Sites – Steve Souders

Tools Used in This Class
• Excel (or similar spreadsheet program)
• Online Testing Tools – webpagetest.org, speedtest.net
• Desktop Testing Tools – your browser, Firebug, netmon, dig,
ping, curl
• Mobile Tools: speedtest app, httpwatch basic, net tools, curl

Class Structure
Schedule
• Start: 9:00 AM
• Break: 10:30-1:45
• Lunch: 12:30-1:15
• Break: 2:30-2:45
• End: 4:00 PM
Agenda
• Section I – What Is Performance?
• Section I – Performance Basics
• Section III – The MPPC Model
• Section IV – Tools & Testing
• Section V – HTML5 & Performance
• Section VI – Mobile Devices

Section I
What is Performance?

What Problem Are We Trying To Solve?
• World-class response times compared to our competitors
• Reliable, predictable performance for users worldwide
across the spectrum of devices
• Efficient use of resources: cost scales linearly with traffic
• Delighted users!

Impact of Performance on Business
• Google
– 500 ms reduces traffic to sites by 20%
• Yahoo!
– 400 ms reduces traffic by 5-9%
• Amazon
– 100 ms reduces revenue by 1%
• Compuware
– 1 sec delay reduces conversion by 7%
11

Who needs
‘Performance’
science anyway?
?
Who cares?

Systemic Qualities In a Nutshell
“Anything you can say about a black box – from the outside”
• Systemic qualities are the “ilities” – physical
features of the system such as capacity,
performance, and scalability
• The SQs correspond to different groups of
stakeholders: users, developers, operators,
organizations
• SQs are the best measure of the quality of the
user’s experience of the system, regardless of
the feature set

The Four Classes of Systemic Qualities
Manifest Qualities - What the users see
• Usability, Performance, Reliability, Availability, Accessibility
Operational Qualities - What the system operators see
• Throughput, Manageability, Security, Serviceability
Developmental Qualities - What developers see
• Buildability, Budgetability, Planability
Evolutionary Qualities - How the system changes over time
• Scalability, Maintainability, Extensibility, Reusability, Portability

The Manifest Systemic Qualities
• Usability reflects the ease with which users can
accomplish their goals
• Performance reflects how much little time users must
wait for actions to complete
• Reliability measures how often the system fails
• Availability measures uptime vs. downtime
• Accessibility measures the systems ability to serve
users regardless of location or physical condition
(including I18N and L10N)

Performance is a Balancing Act
Performance isn’t everything; sometimes we’re called on to
make choices about which systemic qualities have priority over
others. Security v. performance is a common tradeoff – what
would you choose?

What Is Performance?
PERFORMANCE IS RESPONSE TIME

Comparison of Mean, Median, and Mode
Comparison of mean, median and
mode of two log-normal distributions
with different skewness.

Outliers, or Why We Use the Median
• A: skewed to the left
• B: skewed to the right
• C: symmetrical

Statistical Distributions
• Discrete or continuous?
• Mean, median, sigma,
95%?
• Is it reasonable?
|mean – median| <= sigma
• Does it correlate?

Understanding the Margin of Error
• Margin of error at 99% confidence
= 1.29/sqrt(n)
= 0.98/sqrt(n)
= 0.82/sqrt(n)
(where n is the number of sample
data points)
The margin of error is a measure of how close the results are likely to be.

5 Number Reports
A simple way of summarizing a sample
• Shape of the distribution
• Extreme values
• Variance
• Skewness
Draw it!
This is how you get a sense of the data…
Median
1st quartile 3rd quartile
Minimum Maximum

Hands On: Using Curl
• Curl is a text-based HTTP
client for single objects
• We’ll do 10 consecutive
tests of
http://www.twitter.com
• Run the 5 number report
• Plot the results!
• curl -o /dev/null -s -w
%{time_total}n http://www.twitter.com

5 Number Reports in Excel
Excel functions:
Min = MIN(Data Range)
Q1 = QUARTILE(Data Range, 1)
Max = MAX(Data Range)

5 Number Reports in R
Let’s make a 5 number report in R:
R version 3.0.1 (2013-05-16) -- "Good
Sport"
> RT <- c(0, 0, 1, 2, 63, 61, 27, 13)
> fivenum(RT)
[1] 0.0 0.5 7.5 44.0 63.0
http://www.r-project.org/

Operational Research
• Developed during WWII
for managing armies and
supply chains
• A set of rules or ‘laws’ that
describe the operational
aspects of a system.
• Useful for understanding
the performance of any
system
• Utilization Law
• Forced Flow law
• Little’s Law
• Response Time Law

Resources and Queues
Si: Service time
Ri: Queue Residence time
i: Queue length
In general, systems consist of many combined
queues and resources
ResourceQueue
SiRi

The Utilization Law
• The utilization (Ui) of resource i is the
fraction of time that the resource is busy.
• Xi: average throughput of queue i, i.e.
average number of requests that complete
from queue i per unit of time
• Si: average service time of a request at
queue i per visit to the resource
Ui = Xi * Si

Interactive Response time law
IMAGE COURTESY PROF. RAJ JAIN

Hands-on: Using the Response Time Law in
the Real World
Let’s say Facebook’s Web servers can process 10K ‘like’
requests/second, and the number of concurrent users is
600K. If each user waits 5s between requests, how long will
each request take?
R = (N/X) –Z

Hands-on: Using the Response Time Law in
the Real World
Let’s say Facebook’s Web servers can process 10K ‘like’
requests/second, and the number of concurrent users is
600K. If each user waits 5s between requests, how long will
each request take?
R = (N/X) –Z
= 6 * 10e5 / (10 requests/ms) -5 * 10e4ms
= 6 * 10e4 – 5* 10e4 ms
= 1000ms
Facebook needs more servers!

Antipattern: Keyhole optimization
Problem: Optimizing your project
Antipattern: Optimizing *your* project, at
the expense of everyone else!
Pattern: Your project is part of the
system – optimize for the overall system
performance, not just what you can see,
even if that means your part is less-
than-perfectly optimized.

Dimensions of Performance
• Geography
• Network location
• Bandwidth
• Transport Type
• Browser/Device Type
• RT Varies by as much as 50%
• Page Composition
• Client-side rendering and execution effects (JS, CSS)
• Network Transport Effects
• # of Connections, CDN Use

OSI Functionality Summary
Physical
Data Link
Network
Transport
Session
Presentation
Application
Transmit bits
Organize bits into frames
Transmit packets from source to destination
Reliable message delivery end to end
Establish, manage, terminate sessions
Translate, compress, encrypt
Access network resources

All People Seem To Need Data Processing
Physical
Data Link
Network
Transport
Session
Presentation
Application
Processing
Data
Need
To
Seem
People
All

HTTP Connection Flow
Estimated server
processing time
Handshake time
Client’s perceived
response time Request
Response
Connection setup
Client Server
Request transmission
time
Response transmission
time
The more HTTP requests & network roundtrips you require, the slower your
performance will be: Images, CSS, JS, DNS lookups, Redirects, #of packets

The MPPC Model Of Web Performance
End User
HTTP Request
DNS/Network
Resolution
Page
Composition
Payload
Delivery Time
HTTP Request
HTTP Response HTTP ResponseBrowser
Rendering Time
Request
Initiation by
User
This entire cycle, steps 1-4, is repeated once for each external
reference on the page, so for a given page the total time is:
Where n is the number of external page requisites.
T = S Dt1 + Dt2 + Dt3 + Dt4
n+1
S
n+1
t1
t2
t3
t4
T1
Connection Time
T2
Server Duration
T3
Transport Time
T4
Render Time
“Multiple Parallel Persistent Connections”

T1 – Making the Connection
t1= tDNS + tTCP+ tSSL
• Typically a larger part of the E2E
than expected
• Highly variable
• SSL is slow!

Why DNS Matters
• Nothing happens before DNS!
• User does not see anything on their page  waiting
time
• Homework Assignment: create a host file for yourself.
Try your favorite sites without DNS!
• DNS has a great impact on user’s perceptions in HTTP
applications

Interacting with DNS: dig
time

T2 – The Server Duration
• Let (l/m) = dr
• U = (dr)[1-(dr)W]
• X = U * m
• Navg = (dr)[W(dr)W+1 -(W+1)(dr)W+1]
• … so t2 = Navg/X
(The response time law)

T3 – TCP Transport Time
• Single Object:
t3 = Sz/R+2RTT+tidle
For persistent parallel connections:
t3 = (M+1)Si/Ri+[M/kNh]*3SRTTi+tidle
… for 1 base HTML page with M objects, with Si bits, at bandwidth
Ri, k connections per host, and Nh unique hostnames

T4 - What the Browser Does
t4 = S Dtoff(i)
Dtoff = time offset
to parse the HTML, JS, CSS,
and establish the individual
connections
(to different hostnames)
t4 is especially significant for mobile devices!
n
i = 1

Bandwidth Efficiency
Bmax = 1.22*(L)^1/2 * MSS/RTT

Bandwidth, Latency, and All That

Hands-on: Testing DNS Response
times
We’ll use nslookup for this exercise
1. Run 10 nslookup commands for a site (e.g.
www.facebook.com)
2. Observe the response time for the DNS
lookup
3. Calculate statistics for the results
• 5 number report (summary)
• Sketch the distribution
• What can you say about the response times
for DNS?

Antipattern: That’s Outside My Control
It’s never the case that there is ‘nothing you can do’ about a
performance problem.
Antipattern: avoiding solving a performance issue because
you think it’s outside your control. This path leads to
despair.
Pattern: Compensate in some other part of the E2E. Think
outside the box

Let’s Talk Tools
Commercial Performance Services
– Gomez (Compuware)
– Keynote
– AlertSite
– ThousandEyes
• ‘Wholesale’ Testing
– Statistical data for many
page views under different conditions
– Operational testing
– Best for understanding
global and network effects
Page Analysis Tools
– YSlow
– MS Virtual RoundTrip Analyzer,
HTTPWatch, Many Others
– F12 in your browser
• ‘Retail’ Testing
– One Page or App
– Diagnostic
– Best for functional testing

Commercial Testing Services
• Gomez, AlertSite, and Keynote toolsets are similar in many ways
• Synthetic Test Setup
• Test nodes in large datacenters and/or end user’s machines
• Statistical data about response times

Performance Testing Locations
Your Data Centers
QA & Test

HTTP Object Model
Web Page(s)
Page Objects
(or Components)
A Test is a sequence of one or
more URLs for which HTTP
requests will be made.
A Monitor is a set of
predefined Tests to be run at
specific times and places
Each Page Object has 4
associated time segments, t1, t2, t3, t4

Desktop Tools
• Browser Developer Tools
– F12
• Yslow, PageSpeed
• MS Fiddler, VRTA, Full HTTP proxy
• HTTPWatch
• *nix command line tools
– ping, dig, traceroute, curl
• Online Tools
– WebPageTest.Org

Unix Performance Testing Tools
• ping – determine the RTT to a server
• nslookup, dig – retrieve DNS records
• traceroute – analyze TCP traffic routing
• netstat – lists the network connections on this machine
• curl – retrieves an object from a URI using HTTP

WebPageTest.Org
• Free Testing Tool
– Similar to commercial svcs.
– Can help identify problems
in the field that would be
otherwise difficult to find
– You can set up your own
network of WPTO test
nodes in AWS
• More on this in the book!
– Desktop version also

Hands-on: Analyzing Waterfall Diagrams
http://www.webpagetest.org
• Choose a location and a
browser and test:
http://www.yahoo.com

Task-Based Performance Thinking
Welcome
(A)
Inbox
(B)
Bulk
(C)
Compose
(E)
Read
Message
(D) Verify
(F)
Send
Confirm
(G)
P(A,B) = 0.5168
9.85%
35.02%
66.25%10.04%
61.77%
34.52%
58.07%
64.53%
28.04%
34.38%22.30%
Welcome 1400ms
Inbox 2200ms
Bulk 3200ms
…
Exercise: What % of users
follow the path:
A->E->F->G?

Testing Your Competitors for Fun & Profit

Stormcat: Global Performance Testing
• Cannot compare performance data out-of-region
• There are many global factors involved in performance:
• Bandwidth
• ISP
• Infrastructure
• Secular cycles (weeks, holidays, usage patterns)
• The best approach: use the ‘StormCat’ system!
• Best case (Northern California high broadband @3 AM)
• Worst Case (rural Indonesia on VSNL @ 2PM local)
• Divide the range into 5 categories equally spaced between the
best & worst: some locales will be in Cat I, some in Cat II, some in Cat
III, etc.

Antipattern: Design-time Failure
Performance is a design time activity!
Anti-Pattern: Releasing a new or
modified product without testing its
performance
“Bake it in up front!”

A Federated Model for HTML
Core HTML5
HTML
Markup
HTML
Media
IndexDB
Web
Storage
Web
Sockets
Web
Workers
Canvas
2D
Source: Sergey Mavrody c. 2013
This is
XHTML
1.1

The Co-Evolution of HTML, JS, CSS, and
XML
Source: Sergey Mavrody c. 2013
Document Object Model
JavaScript…
JSON…
XML Core
XSLT
XSD
Xpath/XQuery

Tower of Babel: A Problem We Have Yet to
Solve

The Current Browser Landscape
Source: http://www.w3schools.com/browsers/browsers_stats.asp

Hands-on Exercise: Testing Performance
the W3C Way
• Use the Navlet:
http://code.google.com/p/navlet/
Make a bookmark or favorite using the code

Antipattern: We’ll Be Done With This Soon
Performance is an ongoing activity, not fire and forget!
Antipattern: Not treating performance as a property of the
system, or only testing at release time.
Pattern: establishing a long-term performance management
plan as part of your cycle.

The Big Picture – Mobile is Growing

Native Apps v. HTML5 v. Desktop
• Native Apps will run ~ 5x
faster than HTML5
• Roughly 10x slower than
desktop
• HTML5 on the mobile
device can be 50x slower
– 10x from the ARM chip
– 5x from JavaScript

If you’re designing for mobile, it’s safe to assume you’re
going to incur 2000ms of 3G latency.
Mobile Apps Are Slow

Slow Compared to What?
Since 2009 mobile browsers
went from 30x to 5x slower than
desktops
– Better than Moore’s Law
improvement (!)
– JavaScript v. Native code ~ 5x
– 4g/LTE ~ 27% faster than 3g

Mobile JavaScript Performance
• That 5x is in the code
interpretation?
• Typed arrays
• JSON layout
• DOM Manipulation
• Garbage Collection

HTML5: New Features for Mobile
http://mobilehtml5.org/

Delay-tolerant Application Design
• Plan for offline/intermittent
connectivity
• Caching local content
– Local storage
– Don’t be afraid to use sessions
– Use HTTP Caching headers
wisely
• Always have failure modes built-in

The Right Tool For the Right Job
Source: Nick Zakas

Best Practices for Mobile
• Tread lightly on the JavaScript
• Don’t touch the DOM!
• CDNs are less effective due to network challenges
• TTFB is not a good measure of server duration
• Use Web Workers for preloading
• Test performance on different transport types
• Test battery consumption!

4 Takeaways on Mobile Performance
Mobile HTML apps are slow compared to native apps
…but it’s not all about JavaScript
Mobile networking is a big challenge
…so design for delay-tolerance
HTML5 is designed for Mobile
…so use it (wisely)!
Use the right tool for the right job
…including the right design patterns for Mobile

Tools for Mobile Testing
• Speedtest/Ookla
– Variability
– Characteristics of different kinds of networks
• iCurl
– Simple HTTP Operations on your device
• HTTPWatch Basic
– Look at the Waterfall
– Gather detailed data along with iCurl

Hands-on Exercise: Testing Mobile
Performance

Antipattern: It’s The Application Stupid!
T2 (server duration ~ 35% of total E2E
– More on mobile however!
Antipattern: Failing to recognize that the distribution of the
Mobile E2E is very different from a desktop performance
profile
Pattern: Carefully analyze the MPPC numbers for your site
and identify the problems that need to be solved and in
what order.

The 7 Habits of Exceptional Performance
1. Make Performance a Priority
2. Test, Measure, Test Again
3. Learn about the Tools
4. Balance Performance with Features
5. Track Results Over Time
6. Set Targets
7. Ask Questions; Check It for Yourself!
Thanks to Tenni Theurer

Yslow Rules!
• Rule 1 - Make Fewer HTTP
Requests
• Rule 2 - Use a Content Delivery
Network
• Rule 3 - Add an Expires Header
• Rule 4 - Gzip Components
• Rule 5 - Put Style sheets at the Top
• Rule 6 - Put Scripts at the Bottom
• Rule 7 - Avoid CSS Expressions
• Rule 8 - Make JavaScript and CSS
External
• Rule 9 - Reduce DNS Lookups
• Rule 10 - Minify JavaScript
• Rule 11 - Avoid Redirects
• Rule 12 - Remove Duplicate Scripts
• Rule 13 - Configure ETags
• Rule 14 - Make AJAX Cacheable
Source: Stevesouders.com

Every Tool Has Its Place in the Universe

The One Number of Truth
“42”

“…a single user-interface to many large classes of
stored information such as reports, notes, data-bases,
computer documentation and on-line systems help”
WorldWideWeb: Proposal for a HyperText Project
Berners-Lee & Caillau, 1990
About:HTML

Theme of the Work
Ultimately, performance is about respect.

Thank You!
Daniel Austin
Interstellar Travel, Inc.
HTML5 DevConf
May 21, 2014
@daniel_b_austin
da@x.com

Web Performance Bootcamp 2014

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