(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

1. Step By Step Mobile Optimization
Guy Podjarny
@guypod
http://www.guypo.com/ Akamai Confidential

2. 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
Faster ForwardTM ©2012 Akamai

3. 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
Faster ForwardTM ©2012 Akamai

4. Faster ForwardTM
The Tools
©2012 Akamai

5. Waterfall Chart
Doc Complete,
Waterfall Resource
(a.k.a. onload,
Chart (Request/Response)
Start Render Load Time)
Faster ForwardTM ©2012 Akamai

6. 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
Faster ForwardTM ©2012 Akamai

7. “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/
Faster ForwardTM ©2012 Akamai

8. 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
Faster ForwardTM ©2012 Akamai

9. iOS 6 Network Link Conditioner – On Device!
How to Enable:
http://www.neglecte
dpotential.com/201
2/09/ios6-network-
link-conditioner/
Faster ForwardTM ©2012 Akamai

10. Introduction: SLowe’s Commerce
• Demo eCommerce application
• with dedicated Mobile site
• Built on Magento
• Took the Magento Demo Site
• Made some slight modifications
Faster ForwardTM ©2012 Akamai

11. Initial Waterfall Chart
• URL:
www.slowes.org
• Device: iPhone 4
• OS: iOS 6
• Speed: 3G
• Apple’s Definition
• Throttled with Network Link
Conditioner
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12. Initial Filmstrip
• 16 seconds to start render
• 18 seconds to
“Visually Complete”
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13. • Slide about redirects, maybe an eschel drawing?
Step 1:
Redirects Faster ForwardTM ©2012 Akamai

14. 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
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15. Client-Side Detection Often Recommended
Nokia:
Mobify:
Faster ForwardTM ©2012 Akamai

16. 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
Faster ForwardTM ©2012 Akamai

17. JS Redirect => HTTP Redirect
mobileDetect.js Apache
CDN
Fallback:
Inline Script on Desktop page CMS/App Server
Faster ForwardTM ©2012 Akamai

18. 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
Faster ForwardTM ©2012 Akamai

19. Optimization Results - Visual
• ~5 seconds acceleration to start render
Faster ForwardTM ©2012 Akamai

20. Merging Redirect Chains
Only one redirect
• Combine all redirects to one redirect
• Requires combining Application and Mobile logic
Mobile Logic
^/(?:magento/)?(.*) /magento/
Application Logic
Faster ForwardTM ©2012 Akamai

21. 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
Faster ForwardTM ©2012 Akamai

22. 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
Faster ForwardTM ©2012 Akamai

23. Step 2:
Faster ForwardTM
Compression
©2012 Akamai

24. Lack of HTTP Compression (Gzip)
160 KB (!!!)
No Gzip
Faster ForwardTM ©2012 Akamai

25. Solution: Apply Compression
• Gzip compression built into most elements in the stack
• App Server, Web Server, Load Balancer, CDN…
Faster ForwardTM ©2012 Akamai

26. 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
Faster ForwardTM ©2012 Akamai

27. TCP Slow Start (diagrams from John Rauser)
Early TCP Slow Start Delayed ACK
Max Packet Size: 1460 bytes
http://velocityconf.com/velocity2010/public/schedule/detail/11792
Faster Forward
TM
©2012 Akamai

28. TCP Slow Start (diagrams from John Rauser)
• 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
http://velocityconf.com/velocity2010/public/schedule/detail/11792
Faster Forward
TM
©2012 Akamai

29. 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
Faster ForwardTM ©2012 Akamai

30. Step 3: Consolidation
Faster ForwardTM ©2012 Akamai

31. Step 3: Fragmented JS/CSS Files
2 CSS Files
16 JS Files
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32. Step 3: Consolidate CSS & JS Files
Faster ForwardTM ©2012 Akamai

33. Step 3: Consolidate JS/CSS Files - Visual
Fragmented
Consolidated
Consolidation made it worse!
Faster ForwardTM ©2012 Akamai

34. Consolidated vs. Fragmented - Test
• 1 consolidated script
• ~1 MB in size
• 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());
Faster ForwardTM ©2012 Akamai

35. Consolidated vs. Fragmented - Result
Consolidated Fragmented
Fragmented
Consolidated
Starts painting ~5
seconds earlier!
Faster ForwardTM ©2012 Akamai

36. 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/
Faster ForwardTM ©2012 Akamai

37. 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
Faster ForwardTM ©2012 Akamai

38. Step 3a: Simulation – remove combined.js
No Visual
Difference!
Faster ForwardTM ©2012 Akamai

39. 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!!!
Faster ForwardTM ©2012 Akamai

40. Step 4:
Faster ForwardTM Retina Images
©2012 Akamai

41. Retina Images
bg_header_retina.png – 56 KB
1 2
3 4
bg_header.png –
14KB
Faster ForwardTM ©2012 Akamai

42. Lossless Image Compression
• “Image Minification”
Retina: • Sheds bytes without
reducing quality
• Sample techniques:
• Remove Geo data
• Remove Histogram data
Regular: • Remove unused colors
• Replace GIF with PNG-8
• …
Faster ForwardTM ©2012 Akamai

43. 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 Origina Lossless “Desktop” Reduce to Reduce to
l Compression Resolution 320px wide 128px wide
Retina 56KB 48.2KB (14%) 26.6KB (53%) 6.8 KB (88%) 2.2KB (96%)
Regula 14KB 11.5KB (18%) 7KB (50%) 7KB (50%) 2.2KB (85%)
r
Faster ForwardTM ©2012 Akamai

44. Responsive Images
128px,
240px, 6.8 KB 2.9 KB
320px, 10.6 KB
480px, 21.3 KB
Site:
lonelyplanet.com
Device:
iPhone 4
Before:
867 KB
After:
570 KB Full Res, 50.1 KB
Faster ForwardTM ©2012 Akamai

45. Standardizing Responsive Images
@srcset
<picture>
https://github.com/scottjehl/picturefill
Faster Forward
TM
©2012 Akamai

46. 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
Faster ForwardTM ©2012 Akamai

47. Step 4a: Banner Image Compression impact
No Image
Optimization:
Lossy
Compression:
No Retina
Image:
Faster ForwardTM ©2012 Akamai

48. 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
Faster ForwardTM ©2012 Akamai

49. iPhone Optimization: Summary
Faster ForwardTM ©2012 Akamai

50. 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
Faster ForwardTM ©2012 Akamai

51. Interim Summary - Acceleration
Browsing www.slowes.org (including app redirect)
Faster ForwardTM ©2012 Akamai

52. Step 5:
Android
Faster ForwardTM ©2012 Akamai

53. 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
Faster ForwardTM ©2012 Akamai

54. Step 5: Android Test
22 files
Strange gap
(vs. 14 (~200 ms)
on
iPhone)
# Connections
Limit
Both Retina &
regular reqs
Faster ForwardTM ©2012 Akamai

55. Duplicate Requests on Android – Tim Kadlec’s Test
http://timkadlec.com/2012/04/media-query-asset-downloading-results/
Faster Forward
TM
©2012 Akamai

56. Duplicate Requests on Android – Slowe’s
…
…
Faster ForwardTM ©2012 Akamai

57. Duplicate Requests - Solution
• One solution works (almost) everywhere…
• As long as you support media queries…
Faster ForwardTM ©2012 Akamai

58. Step 5a: Eliminate Duplicate Requests - Results
Faster ForwardTM ©2012 Akamai

59. Android
Mind the Gap…
• Theories Strange gap
• It’s the weak mobile device… (~200 ms)
• But it doesn’t happen on iPhone! Chrome
• 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 Chrome for Android
• https://developers.google.com/chrome
/mobile/docs/debugging
• On Nexus 7 Tablet, No gap!
Faster ForwardTM ©2012 Akamai

60. Problem: Translate3D
combined.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”
Faster ForwardTM ©2012 Akamai

61. Step 5b: Remove translate3d calls
Chrome Android
Gap a tiny bit
smaller (~170 ms)
• Results on iPhone, Nexus Tablet remain unchanged
• Issue seems to occur only when Hardware Acceleration is not supported
Faster ForwardTM ©2012 Akamai

62. 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,
Faster ForwardTM ©2012 Akamai

63. Use Analytics to determine YOUR top devices
Google Analytics
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64. Summary
• Summary
Faster ForwardTM ©2012 Akamai

65. 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
Faster ForwardTM ©2012 Akamai

66. Manual FEO
Original Optimized
Original
Original
Original
Original
Original
Original
Original
Faster ForwardTM ©2012 Akamai

67. Automated FEO Pixie Dust
Slow,
Web Generic HTML
Server
• Automates much of the optimization process
• Can’t fix everything, but can save a lot of effort
• Doesn’t replace performance awareness * Visual from
• For example, measuring… Patrick Meenan
Faster ForwardTM ©2012 Akamai

68. 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
Faster ForwardTM ©2012 Akamai

69. Thank You!
Questions?
Step By Step Mobile Optimization
Guy Podjarny
@guypod
http://www.guypo.com/ Akamai Confidential