velocity 2012 - taming the mobile beast
DESCRIPTION
Presentation by Matt Welsh and Patrick Meenan from Google on tools and things to be aware of when developing for the mobile web.TRANSCRIPT
Taming theMobile BeastPatrick Meenan Matt Welsh@patmeenan @mdwelsh
Google, Inc. Google, Inc.
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2.25B Global Internet Users
1.1B Mobile Users
Source: UN/ITU internetworldstats.com
Mobile is huge!
Source: OnDevice Research
For many, a mobile device is the only way to access the Internet
CountryMobile-Only
Internet Users
Egypt 70%
India 59%
South Africa 57%
Indonesia 44%
United States 25%
http://www.flickr.com/photos/43560604@N03/6845754798/
... and growing with respect to desktop
Desktop Web Performance Optimization
Mobile Web Performance Optimization
What we'll cover today:
Getting a handle on mobile web performance
How to collect measurements on mobile devices
Deep dive into mobile web performance issues and common gotchas
Using Chrome for Android's remote debugger
Mobile bookmarklets and other tools
Measurement Tools
Mobitest - www.blaze.io/mobile/
WebPageTest - www.webpagetest.org
Web Page Test now supports Android and
iOS!
Waterfall Basics
Waterfall Components
Waterfalls as seen by HARViewer
DNS TCP Waiting Receiving Lookup Connect for response response
Studying Mobile Waterfalls
Visualizing a mobile website load (brown.edu)
75 seconds!
brown.edu's mobile home page
124 KB, 1800x800background image that is completely
obscured
The web was not designed for mobile
Huge disparity between modern web design and mobile devices...
● Increasingly rich content● Highly dynamic pages● Large amount of JavaScript to manipulate the page, perform asynchronous
work, fetch new content● 3D acceleration, animations, complex graphics
... all sent using a crufty, somewhat broken protocol (HTTP)
The web is not just <b>plain</b> <i>old</i> <blink>HTML</blink>anymore - it is a complete application platform.
● Making a mobile connection: Radio Resource Control
● Browser connection limits
● HTTP Pipelining
● Caching: Browsers vs. embedded HTTP libraries
● Carrier network proxying
● JavaScript execution time differences
Here Be Dragons
Making a Mobile Connection
Typical Mobile Network Performance
Country Average RTT Average Downlink Throughput
Average Uplink Throughput
South Korea 278 ms 1.8 Mbps 723 Kbps
Vietnam 305 ms 1.9 Mbps 543 Kbps
US 344 ms 1.6 Mbps 658 Kbps
UK 372 ms 1.4 Mbps 782 Kbps
Russia 518 ms 1.1 Mbps 439 Kbps
India 654 ms 1.2 Mbps 633 Kbps
Nigeria 892 ms 541 Kbps 298 Kbps
Source: Ookla/Speedtest.net
Compare to typical desktop and WiFi performance:< 50 ms RTT, 5 Mbps throughput in the US
Typical Mobile Network Performance
Country Average RTT Average Downlink Throughput
Average Uplink Throughput
South Korea 278 ms 1.8 Mbps 723 Kbps
Vietnam 305 ms 1.9 Mbps 543 Kbps
US 344 ms 1.6 Mbps 658 Kbps
UK 372 ms 1.4 Mbps 782 Kbps
Russia 518 ms 1.1 Mbps 439 Kbps
India 654 ms 1.2 Mbps 633 Kbps
Nigeria 892 ms 541 Kbps 298 Kbps
Source: Ookla/Speedtest.net
Things are changing fast!LTE promises < 100 ms RTT, 50+ Mbps downlink
Bandwidth Impact
20 Top sites measured in October, 2011
3G
LTE
Latency Impact
20 Top sites measured in October, 2011DSL/Cable Dial
3G
LTE
Making a Radio Connection
Before a cellular device can transmit or receive data, it has to establish a radio channel with the network.
This can take several seconds!
Also, if no data is transmitted or received after a timeout,the channel goes idle, requiring a new channel to be established.
This behavior can wreak havoc on web page load times.
Probing the Radio State Machine
Try this sometime:Build a webpage that loads a small (1KB) image at increasing intervals. Watch how long it takes to load.
Probing the Radio State Machine
Try this sometime:Build a webpage that loads a small (1KB) image at increasing intervals. Watch how long it takes to load.
Here's what it looks like on WiFi:Every image loads in~120 ms
The same thing on T-Mobile:
1 sec delay
2 sec delay
3 sec delay
4 sec delay
5 sec delay
The same thing on T-Mobile:
Between 2 and 3 sec,huge increase in load time
Example 3G Radio Resource Control State Machine
Data from: http://www.eecs.umich.edu/~fengqian/paper/aro_mobisys11.pdf
IDLE
No radioconnection
CELL_DCH
Dedicated radio channel
CELL_FACH
Sharedradio channelTransmit data
Delay: 1-2 sec
Idle for 5 sec
Idle for 12 sec
Buffer size > threshold
The exact delays and idle timeouts depend on the carrier, which equipment they have installed, and how it is configured.
This depends on the network, not the device.
Run your own test now! http://goo.gl/F5sKV
Browser Connection Limits
Browser Connection Limits
The number of parallel connections varies tremendously across mobile browsers.
brown.edu on Android 2.3.5 Gingerbread:
Total of 4 parallel connections
Browser Connection Limits
The number of parallel connections varies tremendously across mobile browsers.
brown.edu on Android 4.0.4 Ice Cream Sandwich:
Looks like 6 connections per domain
The number of parallel connections varies tremendously across mobile browsers.
brown.edu on iOS 5:
Browser Connection Limits
Looks like a lot of parallelism
The number of parallel connections varies tremendously across mobile browsers.
brown.edu on Chrome for Android:
Browser Connection Limits
Also 6 connections per domain
Browser Connection Limits - Summary
Browser Connections Per Domain Total Connections
Android pre-Honeycomb 4 4
Android post-Honeycomb 6 256
iOS 4 4 30
iOS 5 6 52
Chrome for Android 6 256
Caveats: It takes a lot of experimentation and probing to get some of these numbers. iOS results, in particular, should be taken with a grain of salt.
Are more connections always better?
Parallel TCP connections are typically used for two purposes:1) Saturate the network2) Avoid head-of-line blocking
On 3G, more connections are not always a good idea:- Each connection pays the cost of the TCP handshake
(200+ ms on typical 3G links)- Parallel connections can adversely compete for the channel
HTTP Pipelining
HTTP Pipelining
Been in the spec since HTTP/1.1, but largely ignored by desktop browser vendors
Originally thought it would break the Internet
Several requests with identical start times, staggered completion times
Android 2.3.4 (Gingerbread)
Android Browser has been using pipelining for a long time!
Mobile Safari on iOS 5 is using it now, too.
Android ICS and Chrome do not use pipelining, however.
Carrier Network Proxies
Carrier network proxies
Most large carriers do transparent web proxying
Simple page with a 1MB JavaScript file, loaded over WiFi:
976KB, as expected
Carrier network proxies
Most large carriers do transparent web proxying
Simple page with a 1MB JavaScript file, loaded over WiFi:
The same page, loaded on T-Mobile UMTS:
976KB, as expected
7.6KB !?!?!?!!T-Mobile's proxy uses gzip!
JavaScript Execution Time
JavaScript is typically a lot slower on mobile devices.SunSpider benchmark results:
Dual Core Mac Pro: 266.1 ms
Galaxy Nexus (stock browser): 1899 msGalaxy Nexus (Chrome): 1574 ms
iPhone 3GS (iOS 5): 4737 msiPhone 4S (iOS 5): 2200 msiPad 2 (iOS 5): 2097 ms
JavaScript Execution Time
Browser Caching Behavior
Mobile browsers have small caches:
Android 2.3: 8 MBiOS 5: 100 MB, but not persistent!Android Chrome: 250 MB
Compare to typical size of 512 MB or more for desktop browsers.
Not all caches are created equal
Common embedded HTTP libraries often have broken cache behavior!java.net.URLConnectionjava.net.HttpURLConnectionorg.apache.http.client.HttpClient
None of these do any caching at all.
android.webkit.WebViewDoes caching, but does not support redirection.
NSURLRequest - iOS5Does caching, but total cache size is 1 MB for small objects, 40 MB for large objects, no caching for objects > 2MB.
Browsers != Embedded HTTP Libraries
Web Caching on Smartphones: Ideal vs. Reality by Feng Qian, Kee Shen Quah, Junxian Huang, Jeffrey Erman, Alexandre Gerber, Z. Morley Mao, Subhabrata Sen, and Oliver Spatscheck, Proceedings of ACM Mobisys 2012.
Mobile networks have high round-trip-times: hundreds of ms.
Mobile connections can take several seconds to get established.
HTTP pipelining: Coming to iOS, going away in Android.
Beware carrier network proxies.
JavaScript: Ain't so fast.
Not all mobile caches are created equal.
Summary
Roadmap
Getting a handle on mobile web performance
How to collect measurements on mobile devices
Deep dive into mobile web performance issues and common gotchas
Using Chrome for Android's remote debugger
Mobile bookmarklets and other tools
Remote DebuggingChrome on Android
Chrome on Android has full support for Chrome Developer Tools
Remote Debugging Chrome on Android
USB tethering
Desktop Chrome
1) Fire up Chrome on your device
2) Settings > Developer Tools > Enable USB Web debugging
Getting Started
3) On desktop, run:
adb forward tcp:9222 localabstract:chrome_devtools_remote
4) On desktop, visit:
http://localhost:9222
Getting Started
5) Pick the tab you want to debug:
Getting Started
6) You'll initially see a blank window:
Getting Started
7) Hit reload on the phone to get a timeline:
Getting Started
Anything you can do with Chrome Dev Tools on desktop!
● Network events timeline
● Inspect and manipulate the DOM
● Profile CPU and memory usage
● Performance audit
So what can you do with this?
Network events timeline
Each resource is one line
Size, type, time
Timeline
DOMContentevent onload event
Exploring a single request / response
Request Headers
Response headers
Exploring the DOM
Mouse over a DOM element
Element is highlighted on
device!
CPU and memory profiling
CPU and memory profiling
CPU profile of each JS function
CPU and memory profiling
Timeline of page memory usage
Timeline of page events
Size of DOM,#event listeners
Chrome for Android gives you tremendous visibility and control through its remote debugging interface.
Inspect and control the DOM, get timeline information, CPU and memory profiling, and more.
iOS6 is introducing Remote Debugging for Mobile Safari!http://bit.ly/L1zXTXVery similar interface and functionality.
Summary
Mobile Bookmarklets
http://stevesouders.com/mobileperf/mobileperfbkm.php
Meta Bookmarklet
http://getfirebug.com/firebuglite#Stable
Firebug Lite
http://stevesouders.com/mobileperf/pageresources.php
Page Resources
Page Resources - Jdrop
http://mir.aculo.us/dom-monster/
DOMMonster
http://stevesouders.com/mobileperf/docsource.php
Docsource
https://github.com/driverdan/cssess
cssess
https://github.com/Yottaa/NavigationTimingBookmarklethttp://code.google.com/p/navlet/https://github.com/kaaes/timing
Navigation timing bookmarklets
https://bugs.webkit.org/show_bug.cgi?id=61138
webkit Resource Timing
Watch this space:
Other Tools
https://developers.google.com/speed/pagespeed/insights
PageSpeed Insights
http://pcapperf.appspot.com/
PCAP Web Performance Analyzer
Web
tcpdump/packet capture
http://calendar.perfplanet.com/2011/i-see-http/
icy
http://www.iwebinspector.com/
iWebInspector
http://people.apache.org/~pmuellr/weinre/docs/latest/
winre
https://chrome.google.com/webstore/detail/djflhoibgkdhkhhcedjiklpkjnoahfmg
User Agent Switcher Extensions
https://sites.google.com/a/webpagetest.org/docs/using-webpagetest/scripting#TOC-setUserAgent
WebPagetest User-Agent SpoofingsetUserAgent ...setViewportSize <width> <height>navigate www.cnn.com
Monitoring
Measuring mobile web behavior is hard!
Most mobile browsers have no instrumentation interface.
But, things are improving:Chrome for Android and Mobile Safari in iOS6 have a rich debug interface (more later!)
Web Page Test and Blaze.io mobile agents use clever tricks:- Use embedded WebView components, not real browsers- On Android: run tcpdump to capture network packets- On iOS: Instrument pages using JavaScript
Caveat:- Not all events available on iOS (e.g., no DNS lookup or TCP connect times)
Know thy Browser● Real Device
○ Native Browser○ App with embedded UIWebView
● Simulator● Changed User-Agent String in Desktop Browser
Groketh thy Connectivity● Carrier Network
○ Which Carrier○ Carrier Rewriting Proxies
● WiFi○ Connected to....?
Know WHAT and HOW you are measuring
Latency Impact
Real-User Measurement
dvcs.w3.org/hg/webperf/raw-file/tip/specs/NavigationTiming/Overview.html
Google Analytics
Decide what and how you want to measure
Mobile performance deeply impacted by network and browser architecture
Mobile measurement tools have their limits, but are maturing rapidly
This stuff is hard, but it's an exciting time to be alive!
Takeaways
Tuesday, June 26 - Morning Break10:15 – 10:30 : Site Speed Reports in Google Analytics: Measuring your website’s performance
Afternoon Break3:10 – 3:25 : Measuring user perceived latency with Google Analytics Site Speed reports:
hands-on demo and insights3:30 – 3:45 : Async Scripts and why you care, particularly for third-party content
Wednesday, June 27th - Morning Break10:00 – 10:15 : PageSpeed Automatic Optimizations10:15 – 10:30 : PageSpeed Insights for Chrome with mobile support – Demo
Afternoon Break3:10pm – 3:25pm : Measuring Web Performance3:30pm – 3:45pm : HTTP Streaming – discuss the true latency bottleneck with
bi-directional HTTP streaming and “full-duplex HTTP”
Google Booth - Talks
Tuesday, June 25 - Morning Break10:30 - 10:30 : Q&A: Mobile Web Measurement with Matt and Pat
Tuesday, June 26 - Afternoon Break3:10 – 3:50 : Q&A: Your Chrome Wishlist, Suggestions and Questions
Wednesday, June 27 - Morning Break10:00 – 10:30 : Q&A: Performance monitoring with Google Analytics
Google Booth - Office Hours
