QUALCOMM CONFIDENTIAL AND PROPRIETARY

Understanding Mobile Web Browser Performance

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Rajiv VijayakumarQualcomm Incorporated

Topics

§Mobile browser architecture§Mobile network latencies§Android HTTP: Parallel downloads and caching§Power consumption

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SmartPhone Web Browsers

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What is a “WebKit” Browser?

Browser Architecture

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Layout Engine

Browser Architecture

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Browser Architecture

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WebKit

Browser Architecture

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WebKit JavaScriptEngine

Browser Architecture

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WebKit JavaScriptCoreor V8

Browser Architecture

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WebKit

Rendering Networking

JavaScriptCoreor V8

Browser Architecture

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Browser UI

WebKit

Rendering Networking

JavaScriptCoreor V8

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Android

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Android Browser ≠ Chrome

<img src="http://www.qualcomm.com/imgA.jpg">

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<img src="http://www.qualcomm.com/imgA.jpg">

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Time

<img src="http://www.qualcomm.com/imgA.jpg">

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DNS

Time

<img src="http://www.qualcomm.com/imgA.jpg">

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ww

w.q

ualc

omm

.com

96.1

6.97

.9DNS

Time

<img src="http://www.qualcomm.com/imgA.jpg">

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DNS TCP

Time

<img src="http://www.qualcomm.com/imgA.jpg">

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DNSS

YN

SY

N/A

CK

TCP

Time

<img src="http://www.qualcomm.com/imgA.jpg">

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DNS TCP HTTP

Time

<img src="http://www.qualcomm.com/imgA.jpg">

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DNS TCP

GE

T /im

gA.jp

g

HTT

P/1

.1 2

00 O

K

HTTP

Time

<img src="http://www.qualcomm.com/imgA.jpg">

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DNS TCP

GE

T /im

gA.jp

g

HTT

P/1

.1 2

00 O

K

HTTP

Time

Latencies in 3G/4G Networks

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Latencies in 3G/4G Networks

§ Initial connection setup: > 1s (on older 3G)

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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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RTTs at speed of light

§San Diego – New York : ~26ms

§San Diego – Johannesburg : ~110ms

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Every round trip is at least 80-100ms

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DNS TCP HTTP

Every round trip is at least 80-100ms

Including HTTP retrievals from a CDN

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DNS TCP HTTP

DNS

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50

100

150

Seconds0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Histogram of DNS Lookup Times

Source: Data collected over 30 sites (280 domains) on Qualcomm corporate network12

Every new lookup takes 1 RTT + Lookup Time

Domain Sharding

§Use of multiple domains (cdn1.domain.com, cdn2.domain.com)

§Requests may not happen in parallel...

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Parallel Downloads

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cdn1.domain.com/img1A.pngcdn1.domain.com/img1B.pngcdn1.domain.com/img1C.pngcdn1.domain.com/img1D.png

cdn2.domain.com/img2A.pngcdn2.domain.com/img2B.pngcdn2.domain.com/img2C.pngcdn2.domain.com/img2D.png

8 images across 2 domains

cdn1

img1A

cdn2

Browsers typically use 4-6 sockets per host

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img1B

img1C

img1D

img2A

img2B

img2C

img2D

t=0

cdn1

img1A

cdn2

Android

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img1B

img1C

img1D

img2A img2Bimg2C

img2D

cdn1

img1A

cdn2

Android

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img1B

img1C

img1D

img2A img2Bimg2C

img2D

cdn1

img1A

cdn2

Android

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img1B

img1C

img2A

cdn1

img1A

cdn2

Android

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img1B

img1C

img2A

§ “Thread per socket” model

§4 HTTP threads

QUALCOMM CONFIDENTIAL AND PROPRIETARY18 Source: DDMS (from Android SDK) connected to Android 2.3.3 emulator

cdn1

img1A

cdn2

Android

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img1B

img1C

img2A

§ “Thread per socket” model

§4 HTTP threads

cdn1

img1A

cdn2

Android

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img1B

img1C

img2A

§ “Thread per socket” model

§4 HTTP threads

§Only 4 sockets can have outstanding HTTP requests (“active”)

Android

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cdn2

img2A img2Bimg2C

img2D

cdn1

img1A

img1B

img1C

img1D

Android

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cdn2

img2A img2Bimg2C

img2D

Android

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cdn2

img2A img2Bimg2C

img2D

Pipelining

Android

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cdn2

img2A img2Bimg2C

img2D

§Send multiple requests without waiting for each response§ Responses must arrive in order

Pipelining

Android

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cdn2

img2A img2Bimg2C

img2D

§Send multiple requests without waiting for each response§ Responses must arrive in order

§Android pipelines up to 3 requests on each socket

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... ?

Pipelining

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HTTP Caching

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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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Cache Eviction

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Cache Eviction

§What gets evicted to make room?

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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

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Expires:Wed, 09 Jun 2021 21:12:36 GMT

Example of Cache ContentsVisited several sites, read blog posts and linked articles etc.

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Example of Cache ContentsVisited several sites, read blog posts and linked articles etc.sqlite3 webviewCache.db 'select expires from cache order by expires desc;'

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Example of Cache ContentsVisited 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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Example of Cache ContentsVisited 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

Cou

nt

0

50

100

150

200

Expiration Year2010 2020 2030 2040

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§Cache eviction policy affects performance

§Consider real-world cache occupancy when measuring cached page load performance

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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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PowerWhat is the power drawn from the battery while loading a web page?

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28 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

Battery Current (mA)

QUALCOMM CONFIDENTIAL AND PROPRIETARY29 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

11s download (400mA)

10s idle (300mA)Baseline (200 mA)

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

TCP FINs and Power

31 Source: Power measurements made on MDP MSM8655™ running Android 2.3 over commercial 3G network

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

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

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

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/

developer.qualcomm.com/webtech

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Q&A

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.

Disclaimer

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QUALCOMM Incorporated5775 Morehouse Drive

San Diego, CA. 92121-1714U.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.