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(A presentation given at Velocity Conference, London 2012) Mobile Optimization is complicated, and there’s no single silver bullet. Many different bottlenecks take their toll along the way, and while some have a huge impact, others still add up. In this presentation, we’ll take a website and optimize it step by step. In each step we’ll touch on a problem, discuss how to solve it – perhaps in multiple ways – and show the effect of the solution. In the process, we’ll also touch on topics such as measuring mobile performance, differences between browsers, and which pitfalls are common
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Akamai Confidential
Guy Podjarny @guypodhttp://www.guypo.com/
Step By Step Mobile Optimization
©2012 AkamaiFaster ForwardTM
Agenda
• Review Primary Tools• Introduce Demo Mobile Site• Optimize Site in 5 steps
•Describe a problem•Show its impact•Discuss the cause•Try out one or more solutions
• Summary• Q&A
©2012 AkamaiFaster ForwardTM
Disclaimers
• Performance Numbers are never perfect•Numbers vary widely for any given website•In this deck, the numbers are helpers, not absolutes
• This presentation focuses on Mobile•Focus is on problems more common in Mobile websites•I’m intentionally not tackling common Front-End Optimization
• This presentation focuses on dedicated Mobile websites•I won’t be discussing Responsive Web Design (RWD) here•If you want to learn about RWD performance, come back tomorrow
©2012 AkamaiFaster ForwardTM The Tools
©2012 AkamaiFaster ForwardTM
Waterfall ChartWaterfall Chart Start Render
Resource(Request/Response)
Doc Complete,(a.k.a. onload,Load Time)
©2012 AkamaiFaster ForwardTM
WebPageTest
• Free Perf Measurement Tool•www.webpagetest.org
• Open Source•Can be privately installed
• Desktop Browsers•IE 6-9, Chrome, Firefox
• Uses Traffic Shaping•Over faster networks
©2012 AkamaiFaster ForwardTM
“Mobile”-izing WebPageTest with Scripts
• Use Chrome or Firefox as agent •Chrome more similar to real mobile browsers
• Resize window to smartphone size•setviewportsize 320 480•No way to fake a Retina display
• Fake a smartphone user-agent•setUserAgent <Some-Smartphone-UA>•Doesn’t update navigator.userAgent
• Navigate to the relevant site…•navigate http://www.your-site.com/
©2012 AkamaiFaster ForwardTM
Akamai Mobitest
• Free Mobile Web Perf Measurement Tool•http://mobitest.akamai.com/
• Open-Source•http://bit.ly/open-source-mobitest
• Mobile Browsers•iOS, Android
• No Traffic Shaping• Builds on WebPageTest
•Can share a single server
©2012 AkamaiFaster ForwardTM
iOS 6 Network Link Conditioner – On Device!
How to Enable:
http://www.neglectedpotential.com/2012/09/ios6-network-link-conditioner/
©2012 AkamaiFaster ForwardTM
Introduction: SLowe’s Commerce
• Demo eCommerce application •with dedicated Mobile site
• Built on Magento•Took the Magento Demo Site•Made some slight modifications
©2012 AkamaiFaster ForwardTM
Initial Waterfall Chart
• URL:www.slowes.org
• Device: iPhone 4• OS: iOS 6• Speed: 3G
•Apple’s Definition•Throttled with Network Link
Conditioner
©2012 AkamaiFaster ForwardTM
Initial Filmstrip
• 16 seconds to start render• 18 seconds to
“Visually Complete”
©2012 AkamaiFaster ForwardTM
• Slide about redirects, maybe an eschel drawing?
Step 1: Redirects
©2012 AkamaiFaster ForwardTM
JavaScript Redirect - The Good
mobileDetect.js:
• Client-side browser detection• Easy to deploy
•Compared to server changes
• “Future Friendly” •Can test screen width alongside UAs
©2012 AkamaiFaster ForwardTM
Client-Side Detection Often Recommended
Nokia:
Mobify:
©2012 AkamaiFaster ForwardTM
JavaScript Redirect – The Bad
• Slow! •Redirect only happens after
JS is downloaded and executed
• Unnecessary download of other resources•Some above the JS in the HTML•Some downloaded early by speculative parser
©2012 AkamaiFaster ForwardTM
JS Redirect => HTTP Redirect
mobileDetect.js Apache
Fallback:Inline Script on Desktop page
CDN
CMS/App Server
©2012 AkamaiFaster ForwardTM
Optimization Results - Waterfall
• Real page starts loading after ~1.5 secs vs 5.5 secs•~4 Seconds saved
• No downloading of excess CSS and JS
• All Good: Less requests, less bytes, less delay
©2012 AkamaiFaster ForwardTM
Optimization Results - Visual
• ~5 seconds acceleration to start render
©2012 AkamaiFaster ForwardTM
Merging Redirect Chains
• Combine all redirects to one redirect
• Requires combining Application and Mobile logic
Mobile Logic
Application Logic
^/(?:magento/)?(.*)
Only one redirect
/magento/
©2012 AkamaiFaster ForwardTM
Avoiding Redirects: Serving Client-Specific HTML
• Instead of redirecting, return client-aware HTML•Same URL returns HTML by client•Caution: Caching appliances & CDNs must be tuned•Requires consistent paths across all variations
No Redirect
©2012 AkamaiFaster ForwardTM
Step 1: Conclusions
• Redirects have a real cost•Especially in high latency mobile networks
• HTTP Redirects are much faster than JS Redirects•Use HTTP Redirects•Use JS Redirects as backup only
• 1 Redirect is faster than… more than 1 redirect•Merge redirect chains whenever possible
• No redirects are faster than even 1 redirect!•Consider serving different HTML to different clients on one site
©2012 AkamaiFaster ForwardTM
Step 2: Compression
©2012 AkamaiFaster ForwardTM
Lack of HTTP Compression (Gzip)
160 KB (!!!)No Gzip
©2012 AkamaiFaster ForwardTM
Solution: Apply Compression
• Gzip compression built into most elements in the stack•App Server, Web Server, Load Balancer, CDN…
©2012 AkamaiFaster ForwardTM
Compression matters more on Mobile!
• Mobile websites have less images•JS & CSS account for more of the bytes•Therefore, more of the bytes is compressible•Therefore, compression matters more on Mobile.
• (Practically) all mobile browsers support compression•Kinda true on desktop these days
• Download bandwidth on mobile is smaller than broadband• Latency on mobile is higher on broadband
©2012 AkamaiFaster ForwardTM
TCP Slow Start (diagrams from John Rauser)
Slow Start
Max Packet Size: 1460 bytes
http://velocityconf.com/velocity2010/public/schedule/detail/11792
Delayed ACKEarly TCP
©2012 AkamaiFaster ForwardTM
TCP Slow Start (diagrams from John Rauser)
http://velocityconf.com/velocity2010/public/schedule/detail/11792
• Time to deliver ~72KB:•Fiber (4ms RTT): ~24ms•DSL (50ms RTT): ~300ms•3G (200ms RTT): 1.2 seconds (!!!)
• Time to deliver ~300KB:•Fiber (4ms RTT): ~40ms•DSL (50ms RTT): ~500ms•3G (200ms RTT): 2 seconds (!!!)
• Slow-Start is per connection
©2012 AkamaiFaster ForwardTM
Step 2: Conclusions
• Compression is a critical optimization• Easy to implement, especially in Mobile
•All mobile browsers (that you care about) support it
• Especially important on Mobile•Compressible content (JS,CSS…) accounts for a bigger part of the page•High latency makes large download slow•High packet loss makes large downloads unbearable
©2012 AkamaiFaster ForwardTMStep 3: Consolidation
©2012 AkamaiFaster ForwardTM
Step 3: Fragmented JS/CSS Files
2 CSS Files
16 JS Files
©2012 AkamaiFaster ForwardTM
Step 3: Consolidate CSS & JS Files
©2012 AkamaiFaster ForwardTM
Step 3: Consolidate JS/CSS Files - Visual
Consolidation made it worse!
Fragmented
Consolidated
©2012 AkamaiFaster ForwardTM
Consolidated vs. Fragmented - Test
• 10 scripts, with IDs from 1 - 10• Each script weights ~100 KB• Each script ends with:
•document.write('Processed file ID @, time is ' + new Date());
• 1 consolidated script• ~1 MB in size
©2012 AkamaiFaster ForwardTM
Consolidated vs. Fragmented - ResultFragmentedConsolidated
Fragmented
Consolidated
Starts painting ~5 seconds earlier!
©2012 AkamaiFaster ForwardTM
Consolidation & Progressive Processing
• Browsers only process JavaScript & CSS when fully loaded•Unlike HTML, which is processed (roughly) as soon as it arrives
• Consolidation delays the first script execution, CSS evaluation•Especially with many scripts of varying sizes•Possibly not always true for CSS
• This means Consolidation often delays dynamic requests•Generated by scripts, thus not seen until execution•Often results in a slower page
• Making consolidating “streaming” is doable, but hard•http://www.guypo.com/uncategorized/consolidation-not-simple-addition/
©2012 AkamaiFaster ForwardTM
Step 3a: Async Scripts
• Defer external script execution to onload•Often useful to defer download as well!
• Replace dependent inline scripts with event handlers•Invoked in “onload” of appropriate external script •No need to touch inline scripts with no dependencies
• Complications:•Scripts required for basic page functionality•Scripts that use document.write()•3rd party scripts (you don’t know what they use…)
• Complications not as common in simpler mobile websites
©2012 AkamaiFaster ForwardTM
Step 3a: Simulation – remove combined.js
No Visual Difference!
©2012 AkamaiFaster ForwardTM
Step 3: Conclusions
• Consolidation is good and bad•Good: Reduces roundtrips•Bad: Hurts caching, progressive processing
• Consolidate with Care•Merge small files together, especially if functionally related•If you can, use Adaptive and Streaming Consolidation
•http://www.guypo.com/uncategorized/consolidation-not-simple-addition/
• Procrastinate - Defer as much as you can•Often easier to do on Mobile websites
• Measure!!!
©2012 AkamaiFaster ForwardTM
Step 4: Retina Images
©2012 AkamaiFaster ForwardTM
Retina Images
bg_header_retina.png – 56 KB
bg_header.png – 14KB
1 2
43
©2012 AkamaiFaster ForwardTM
Lossless Image Compression
Retina:
Regular:
• “Image Minification”• Sheds bytes without
reducing quality• Sample techniques:
•Remove Geo data•Remove Histogram data•Remove unused colors•Replace GIF with PNG-8•…
©2012 AkamaiFaster ForwardTM
Lossy Image Compression
• Reduce quality without hurting User Experience• For Desktop, reduce to high-end screen resolution• For Mobile, reduce to display size & resolution
•Known as “Responsive Images”
Image Original
LosslessCompression
“Desktop” Resolution
Reduce to 320px wide
Reduce to 128px wide
Retina 56KB 48.2KB (14%) 26.6KB (53%) 6.8 KB (88%) 2.2KB (96%)
Regular
14KB 11.5KB (18%) 7KB (50%) 7KB (50%) 2.2KB (85%)
Image Original
LosslessCompression
Retina 56KB 48.2KB (14%)
Regular
14KB 11.5KB (18%)
Image Original
LosslessCompression
“Desktop” Resolution
Retina 56KB 48.2KB (14%) 26.6KB (53%)
Regular
14KB 11.5KB (18%) 7KB (50%)
Image Original
LosslessCompression
“Desktop” Resolution
Reduce to 320px wide
Retina 56KB 48.2KB (14%) 26.6KB (53%) 6.8 KB (88%)
Regular
14KB 11.5KB (18%) 7KB (50%) 7KB (50%)
©2012 AkamaiFaster ForwardTM
Responsive Images
128px, 2.9 KB240px, 6.8 KB
320px, 10.6 KB
480px, 21.3 KB
Full Res, 50.1 KB
Site:lonelyplanet.comDevice:iPhone 4Before: 867 KBAfter: 570 KB
©2012 AkamaiFaster ForwardTM
Standardizing Responsive Images
@srcset
<picture>
https://github.com/scottjehl/picturefill
©2012 AkamaiFaster ForwardTM
Responsive Images - Summary
• Smaller screens don’t benefit from high quality images• Solution: Respond to screen size by reducing image quality• Screen size detection usually done on client side
•But same technique can be used on server-side•Examples: Sencha.io Src (Free), Akamai EIM (Commercial)
• Don’t forget CSS background images!•Implementation is easier – with a few catches we’ll discuss later…
• Optional: Lazy-load higher quality images •May defer them to onload•May load them on demand
©2012 AkamaiFaster ForwardTM
Step 4a: Banner Image Compression impact
Lossy Compression:
No Retina Image:
No Image Optimization:
©2012 AkamaiFaster ForwardTM
Step 4: Conclusions
• Mobile screen size & resolution are an opportunity & a threat•Opportunity: Reduce bytes on smaller screens•Threat: Using Retina images broadly
• Lossless Image Compression should be a given•No trade-offs, just do it.
• Lossy Comp/Responsive Images avoid excessive quality•Avoid images too big for a user to appreciate (on this device)•Optionally load low quality images first, high quality images at onload
• Measure!!!•Show your designers the UX impact of every image quality change
©2012 AkamaiFaster ForwardTM
iPhone Optimization: Summary
©2012 AkamaiFaster ForwardTM
Interim Summary - Actions
• Step 1: Improved Redirects•Replaced JS Redirect with HTTP Redirect•Merged redirect chains
• Step 2: Applied HTTP Compression• Step 3: Consolidated JavaScript and CSS files
•Async’d JavaScript files too
• Step 4: Compressed Images•Lossless Compression•Lossy Compression•No Retina Images
©2012 AkamaiFaster ForwardTM
Interim Summary - Acceleration
Browsing www.slowes.org (including app redirect)
©2012 AkamaiFaster ForwardTM
Step 5: Android
©2012 AkamaiFaster ForwardTM
Testing on Android
• No network Throttling on-device•iOS had the same problem until a few weeks ago (with iOS 6)
• Alternative: Tether to laptop, throttle there•Instructions on how to tether: http://pcapperf.appspot.com/•Unfortunately, newer Androids can’t connect through laptop
• Realistic alternative: Test w/out throttling•No 3G load times, but can find interesting data in Waterfall chart•Use Real User Measurement to monitor real world numbers•Use Mobitest for Android Browser, Remote Debugging for Chrome
©2012 AkamaiFaster ForwardTM
Step 5: Android Test
Strange gap(~200 ms)
# Connections Limit
22 files(vs. 14
on iPhone)
Both Retina & regular reqs
©2012 AkamaiFaster ForwardTM
Duplicate Requests on Android – Tim Kadlec’s Test
http://timkadlec.com/2012/04/media-query-asset-downloading-results/
©2012 AkamaiFaster ForwardTM
Duplicate Requests on Android – Slowe’s
…
…
©2012 AkamaiFaster ForwardTM
Duplicate Requests - Solution
• One solution works (almost) everywhere…•As long as you support media queries…
©2012 AkamaiFaster ForwardTM
Step 5a: Eliminate Duplicate Requests - Results
©2012 AkamaiFaster ForwardTM
Mind the Gap…Strange gap(~200 ms)
• Theories•It’s the weak mobile device…
•But it doesn’t happen on iPhone!•It’s the old Android browser…
•Harder to test Chrome for Android•Let’s test with desktop Chrome
•Ok, let’s test on Chrome for Android…•Using Remote Debugging
•https://developers.google.com/chrome/mobile/docs/debugging
•On Nexus 7 Tablet, No gap!
Android
Chrome
Chrome for Android
©2012 AkamaiFaster ForwardTM
Problem: Translate3Dcombined.css
“The translate3d() CSS function moves the position of the element in the 3D space. This transformation is characterized by a 3-dimension vector whose coordinates define how much it moves in each direction”
©2012 AkamaiFaster ForwardTM
Step 5b: Remove translate3d calls
Chrome
• Results on iPhone, Nexus Tablet remain unchanged•Issue seems to occur only when Hardware Acceleration is not supported
Gap a tiny bit smaller (~170 ms)
Android
©2012 AkamaiFaster ForwardTM
Step 5: Conclusions
• Not all (mobile) browsers/devices are the same•Even if they’re WebKit based
• Don’t optimize things you’re not doing•Especially if you’re using hacks to do the optimization
• Say it with me: MEASURE!!!•In Mobile, you have to test on multiple devices•Android devices vary by OS Version, OEM, device…•Use analytics to find your top clients,
©2012 AkamaiFaster ForwardTM
Use Analytics to determine YOUR top devices
Google Analytics
©2012 AkamaiFaster ForwardTM
• Summary
Summary
©2012 AkamaiFaster ForwardTM
What have we done?
• We optimized one home page in 5 steps:•Step 1: Redirect Optimization•Step 2: HTTP Optimization•Step 3: JS/CSS Optimization•Step 4: Image Optimization•Step 5: Cross-Device Optimization
• We MEASURED during each step•Assuming less-than-stellar network conditions
• We made the page ~5x faster
©2012 AkamaiFaster ForwardTM
Original
Original
Manual FEO
Optimized
OriginalOriginal
OriginalOriginal
OriginalOriginal
©2012 AkamaiFaster ForwardTM
Automated FEO
Web Server
Slow, Generic HTML
Optimize
d HTMLPixie Dust
• Automates much of the optimization process•Can’t fix everything, but can save a lot of effort
• Doesn’t replace performance awareness•For example, measuring…
* Visual from Patrick Meenan
©2012 AkamaiFaster ForwardTM
Final Words
• A mobile page with few images != A fast page• Mobile Site Common Pitfalls:
•Slow and repeated redirects•Excess JavaScript & CSS
• Mobile Site Opportunities:•Reduce image size: Smaller Screen •Defer JS: Simpler content can be visually complete without it
• Measuring Is Critical•Test on different devices and browsers•Should be built into QA & Build System regression tests
Akamai Confidential
Guy Podjarny @guypodhttp://www.guypo.com/
Step By Step Mobile Optimization
Thank You!Questions?