Slides from my presentation at Velocity 2011.

1. Understanding Mobile Web
Browser Performance
Rajiv Vijayakumar
Qualcomm Incorporated
QUALCOMM CONFIDENTIAL AND PROPRIETARY
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2. Topics
§ Mobile browser architecture
§ Mobile network latencies
§ Android HTTP: Parallel downloads and caching
§ Power consumption
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3. SmartPhone Web Browsers
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4. What is a “WebKit” Browser?
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5. Browser Architecture
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6. Browser Architecture
Layout Engine
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7. Browser Architecture
WebKit
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8. Browser Architecture
JavaScript
WebKit
Engine
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9. Browser Architecture
JavaScriptCore
WebKit
or V8
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10. Browser Architecture
JavaScriptCore
WebKit
or V8
Rendering Networking
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11. Browser Architecture
Browser UI
JavaScriptCore
WebKit
or V8
Rendering Networking
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12. Android
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13. Android Browser ≠ Chrome
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14. <img src="http://www.qualcomm.com/imgA.jpg">
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15. <img src="http://www.qualcomm.com/imgA.jpg">
Time
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16. <img src="http://www.qualcomm.com/imgA.jpg">
DNS
Time
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17. <img src="http://www.qualcomm.com/imgA.jpg">
DNS
Time
96.16.97.9
www.qualcomm.com
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18. <img src="http://www.qualcomm.com/imgA.jpg">
DNS TCP
Time
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19. <img src="http://www.qualcomm.com/imgA.jpg">
DNS TCP
Time
SYN
SYN/ACK
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20. <img src="http://www.qualcomm.com/imgA.jpg">
DNS TCP HTTP
Time
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21. <img src="http://www.qualcomm.com/imgA.jpg">
DNS TCP HTTP
Time
HTTP/1.1 200 OK
GET /imgA.jpg
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22. <img src="http://www.qualcomm.com/imgA.jpg">
DNS TCP HTTP
Time
HTTP/1.1 200 OK
GET /imgA.jpg
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23. Latencies in 3G/4G Networks
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24. Latencies in 3G/4G Networks
§ Initial connection setup: > 1s (on older 3G)
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25. Latencies in 3G/4G Networks
§ Initial connection setup: > 1s (on older 3G)
§ Round trip time (RTT): 80ms or higher (typically)
§ 100 - 200ms common
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26. RTTs at speed of light
§ San Diego – New York : ~26ms
§ San Diego – Johannesburg : ~110ms
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27. Every round trip is at least 80-100ms
DNS TCP HTTP
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28. Every round trip is at least 80-100ms
DNS TCP HTTP
Including HTTP retrievals from a CDN
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29. DNS
Every new lookup takes 1 RTT + Lookup Time
Histogram of DNS Lookup Times
150
100
50
0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Seconds
12 Source: Data collected over 30 sites (280 domains) on Qualcomm corporate network

30. Domain Sharding
§ Use of multiple domains
(cdn1.domain.com, cdn2.domain.com)
§ Requests may not happen in parallel...
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31. Parallel Downloads
8 images across 2 domains
cdn1.domain.com/img1A.png cdn2.domain.com/img2A.png
cdn1.domain.com/img1B.png cdn2.domain.com/img2B.png
cdn1.domain.com/img1C.png cdn2.domain.com/img2C.png
cdn1.domain.com/img1D.png cdn2.domain.com/img2D.png
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32. Browsers typically use 4-6 sockets per host
img1A
img1B
img1C
cdn1
img1D
img2A
img2B
img2C
cdn2
img2D
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t=0

33. Android
img1A img1D
img1B
img1C
cdn1
img2A img2B
img2C
img2D cdn2
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34. Android
img1A img1D
img1B
img1C
cdn1
img2A img2B
img2C
img2D cdn2
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35. Android
img1A
img1B
img1C
cdn1
img2A
cdn2
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36. Android
img1A § “Thread per socket” model
img1B
cdn1
img1C § 4 HTTP threads
img2A
cdn2
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37. QUALCOMM CONFIDENTIAL AND PROPRIETARY
18 Source: DDMS (from Android SDK) connected to Android 2.3.3 emulator

38. Android
img1A § “Thread per socket” model
img1B
cdn1
img1C § 4 HTTP threads
img2A
cdn2
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39. Android
img1A § “Thread per socket” model
img1B
cdn1
img1C § 4 HTTP threads
§ Only 4 sockets can have
img2A
outstanding HTTP requests
cdn2 (“active”)
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40. Android
img1A img1D
img1B
img1C
cdn1
img2A img2B
img2C
img2D cdn2
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41. Android
img2A img2B
img2C
img2D cdn2
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42. Android
img2A img2B
img2C
img2D cdn2
Pipelining
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43. Android
img2A img2B
img2C
img2D cdn2
Pipelining
§ Send multiple requests without waiting for each
response
§ Responses must arrive in order
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44. Android
img2A img2B
img2C
img2D cdn2
Pipelining
§ Send multiple requests without waiting for each
response
§ Responses must arrive in order
§ Android pipelines up to 3 requests on each socket
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45. Pipelining
§ Not supported, or not enabled by default on most major
browsers
§ Historically caused problems (e.g. due to badly behaving
proxies)
§ Millions of Android devices actively using pipelining
§ Time to revisit... ?
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46. HTTP Caching
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47. HTTP Caching
§ WebKit maintains a memory cache
§ Default size = 8 MB
§ Android has a persistent (file system) HTTP cache
§ Default size = 6 MB
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48. Cache Eviction
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49. Cache Eviction
§ What gets evicted to make room?
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50. Cache Eviction
§ What gets evicted to make room?
§ Android policy: Prioritize base on expiration date
§ Far future expiration dates have higher priority
§ Evict lowest priority items first
Expires:Wed, 09 Jun 2021 21:12:36 GMT
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51. Example of Cache Contents
Visited several sites, read blog posts and linked articles etc.
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52. Example of Cache Contents
Visited several sites, read blog posts and linked articles etc.
sqlite3 webviewCache.db 'select expires from cache order by expires desc;'
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53. Example of Cache Contents
Visited several sites, read blog posts and linked articles etc.
sqlite3 webviewCache.db 'select expires from cache order by expires desc;'
Expiration Year
2036
2035
...
2011
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54. Example of Cache Contents
Visited several sites, read blog posts and linked articles etc.
sqlite3 webviewCache.db 'select expires from cache order by expires desc;'
200
Expiration Year
150
2036
Count
2035 100
... 50
2011
0
2010 2020 2030 2040
24 Expiration Year

55. § Cache eviction policy affects performance
§ Consider real-world cache occupancy when measuring
cached page load performance
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56. Caveats
§ Devices can (and do!) differ from stock Android
§ Differences in:
§ Number of HTTP threads
§ Cache size and eviction algorithm
§ etc.
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57. Power
What is the power drawn from the battery while loading a
web page?
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58. Battery Current (mA)
28 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

59. 11s download (400mA)
Baseline (200 mA) 10s idle (300mA)
QUALCOMM CONFIDENTIAL AND PROPRIETARY
29 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

60. Power
§ Any network traffic brings up the radio for several seconds
§ Network dormancy timer: typically 10-15 seconds
§ Use long periods for any periodic Ajax calls etc.
30 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

61. TCP FINs and Power
31 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

62. TCP FINs and Power
§ Android closes TCP sockets after ~6s of inactivity
§ Sockets get closed at different times
31 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

63. TCP FINs and Power
§ Android closes TCP sockets after ~6s of inactivity
§ Sockets get closed at different times
§ Every socket close generates a TCP FIN
§ Extends the dormancy timer
§ Keeps the modem on for a 1-bit communication
31 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

64. TCP FINs and Power
§ Android closes TCP sockets after ~6s of inactivity
§ Sockets get closed at different times
§ Every socket close generates a TCP FIN
§ Extends the dormancy timer
§ Keeps the modem on for a 1-bit communication
§ Optimization: close all sockets after page load completes
31 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

65. JavaScript Performance
§ SunSpider benchmark numbers have improved dramatically
in recent years
§ Android (Jun 2011) < 2.5s
§ Desktop Chrome (Sep 2008) ~2.8 s
32 Source: http://ejohn.org/blog/javascript-performance-rundown/

66. developer.qualcomm.com/webtech
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67. Q&A
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68. Disclaimer
QUALCOMM Incorporated
5775 Morehouse Drive
San Diego, CA. 92121-1714
U.S.A.
Copyright © 2011 Qualcomm Incorporated.
All rights reserved.
Not to be used, copied, reproduced in whole or in part, nor its contents revealed in any manner to others
without the express written permission of Qualcomm.
Qualcomm and MSM8655 are trademarks of Qualcomm Incorporated, registered in the United States.
Other product and brand names may be trademarks or registered trademarks of their respective owners.
Nothing in these materials is an offer to sell any of the components or devices referenced herein. Certain
components for use in the U.S. are available only through licensed suppliers. Some components are not
available for use in the U.S.
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