understanding and measuring web performance

Understanding and measuring web performance

Bogdan Gâza

CodeCamp NOV’12 Bogdan Gâza

Mechanic at

Monday, November 19, 12

Agenda

What is

Measuring

Take aways

Bogdan Gâza

} web performance

CodeCamp NOV’12


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Agenda

What is

Measuring

Take aways } web performance

CodeCamp NOV’12


Web performance is the time perceived by an user when loading a web resource.

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Click Load

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Human perception of time is bothsubjective and variable

actual

expected

perceived

remembered

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Delay User reaction

0 - 100 ms Instant

0 - 300 ms Feels sluggish

0 - 1000 ms Machine is working

1s+ Mental context switch

10s+ I’ll come back later

Human perception of time is bothsubjective and variable

CodeCamp NOV’12


Amazon TechO(n) Bogdan GâzaBogdan Gâza

DelayDistinct Queries Satisfaction

Time To Interaction

1000 ms - 0.7% -1.6% 1900 ms

2000 ms -1.8% -3.8% 3100ms

en.oreilly.com/velocity2009/public/schedule/detail/8523

Bing - negative impacts when adding delay

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Amazon TechO(n) Bogdan GâzaBogdan Gâza

Importance of performance

Yahoo! - 400ms slower6% drop in full-page traffic

Firefox Download page

- 2.2s faster avg page load time

+15.4% more downloads

CodeCamp NOV’12


Bogdan Gâza

What is

Measuring

Take aways } web performance

Agenda

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Click Load

Measuring web performance

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Click Load

Short life of a http request

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Click

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Click

Unload

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Click

Unload DNS

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Click

Unload DNS TCP

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Click

Unload DNS TCP REQUEST

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Click

Unload DNS TCP REQUEST RESPONSE

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PROCESSING ONLOAD

Load

REQUEST RESPONSE

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Click Load

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Click Load

clickToPageLoaded

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Click ?

Key metrics

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Key metrics

Click


Time to First Byte

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PROCESSING ONLOAD

Load

REQUEST RESPONSE

Render Start Time

Key metrics

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PROCESSING ONLOAD

Load

REQUEST RESPONSE

DomContentLoaded

Key metrics

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PROCESSING ONLOADREQUEST RESPONSE

Page LoadedTime

Key metrics

Load

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Click

High Level Metrics

Load BusinessRelevantEvent

clickTo BusinessRelevantEvent

aboveTheFold

FirstClick

FirstScroll

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High Level Metrics

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clickToFirstTweet


Aggregation

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AVG

Average is not always relevant

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Context

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Time of day Operating System

Browser Antivirus

Location Devise

Connection type Resolution

Latency ...

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Measuring web performance

Subjective (qualitative) Objective (quantitative)

Focus Groups JavaScript

Case Studies Navigation timings

Interviews Browser Extensions

... Web Server Mods

... Network sniffing

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Measuring web performance using JavaScript

unLoadEventstart timestamp

Store start in a cookie

Load nextpage

loadEventstop timestamp

Send a beaconbeacon.gif?time=PLT

Page Load Time (PLT)

stop - start

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Pro’s Con’s

Simple JavaScript

Simple Custom Metrics Accurate for the 2nd page

... Observer effect

Measuring web performance using JavaScript

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Click


Measuring web performance using Navigation Timings

navigationStart

domainLookupStart

domainLookupEnd

connectStart

connectEnd

...

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PROCESSING ONLOAD

Load

REQUEST RESPONSE


domContentLoaded

domLoadComplete

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CodeCamp NOV’12


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Pro’s Con’s

Simple JavaScript

Lots of metrics Page Level Only

Accurate Needs browser support


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Measuring web performance using Browser Extensions

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Pro’s Con’s

Very complete metrics Getting users to install it

No JavaScript Not natively cross browser

Not only page level ...

Measuring web performance using Browser Extension

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Measuring web performance using a web server mod

Web server

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Web server

Performance module

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Web server

Performance moduleRegisters

timestamps

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Web server

Performance moduleRegisters

timestamps

Collects &aggregates

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Pro’s Con’s

Good for measuring back-end performance Limited metrics

Can be easy to deployPossible web server

performance hits

... Concept of a page is problematic

Measuring web performance using Web Server mod

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Net

wor

k Web app

CodeCamp NOV’12

Measuring web performance using network sniffing


Bogdan Gâza

Web app

Web perf applianceNet

wor

k

CodeCamp NOV’12



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Web app

Web perf appliance

Promiscuous mode

Assembles packets

Assembles http into pages

Collects data

Net

wor

k

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Pro’s Con’s

No observer effect Limited metrics

Used in appliance basedsolutions Not cloud friendly

... Concept of a page is problematic


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Take aways

Performance is subjective, context is critical

Observations vs Experiments

W3C Nav Timings

Speed (latency) an important feature

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Q/A

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Thanks!

CodeCamp NOV’12


understanding and measuring web performance

Documents

short life

web resource

web server mods

beacon page load

human perception of

s faster avg page load

key metricsrender

key metricstime