Delivering the Best Web Experience for Embedded Devices. Presentation held during Qt Developer Days 2009. http://qt.nokia.com/developer/learning/elearning

1. Accelerating performance on Qt and
WebKit for the MIPS architecture
Delivering the Best Web Experience
for Embedded Devices

2. Agenda
• MIPS Introduction
• Emerging Trends
• Web Connectivity
• JIT Optimizations for WebKit
• Benchmarks
• Summary

3. MIPS Technologies Overview
MIPS®: Number One Processor
Architecture for the Digital Home
MIPS develops &
licenses processor IP
for the embedded
semiconductor market
Hundreds of licenses
Billions of units shipped
At the core of today’s most
innovative digital consumer products

4. MIPS Segments & Markets
Consumer Communication
DTV DVD STB VoIP WiFi Modem/RG
DPF
Home Home
NAS
Entertainment Networking
DMA
DSC/DVC
Printers &
Copiers
Personal Other
Entertainment Segments
Internet
Games
Infra
PND/PMP MID/Netbook Telematics Appliances
Mobile Microcontrollers, Enterprise

5. MIPS Processors: Owning “The Digital Home”
-The Growth Sector of Semiconductors for 2009-
End Market Share
& Customers
Digital TV 60%
Set Top Box
-Cable 72%
-IPTV 75%
Our customers include
DVD
-Blu-ray 75%
-DVD 72%
Digital Camera 31%
Mobile TV
& GPS PMP 60%

6. MIPS 32-Bit Processor Core Families
1004K: Multi-threaded (34K), Multiprocessor (1-4 cores) Broad range
Coherence Management Unit 1004K of
1.3+ GHz (40nm), 1.5DMIPS/MHz/Core
synthesizable
processors,
74K: Superscalar
15-stage pipeline optimized for
1.1 GHz in 65nm (prod’n frequency) 74K low-power
Up to 2.7GHz in 40nm convergent
consumer
34K: Multi-threading 34K
multimedia
applications
24KE: DSP extensions
24KE
24K: 8-stage pipeline 800 MHz
(65nm) 24K
m M14Kc
i
c M14Kc
4KE: Cache, MMU 4KE r
o
M4K: MCU, Low Cost M
M4K M14K
I
P
S
4KS: Security 4KS microMIPS, MIPS32
Reduced interrupt latency
AHB, advanced debug

7. Agenda
• MIPS Introduction
• Emerging Trends
• Web Connectivity
• JIT Optimizations for WebKit
• Benchmarks
• Summary

8. MIPS in Converging Devices
Universal Media
Player
IP Phone
Networked
Multi-Protocol Media Tank
IP Phone
IPOD Video
LCD TV
Recorder
with Widgets
IP Set-top Box
HD
Home Entertainment Camcorder
Device Movie Player STB
Portable Media
Player
Networked Digital
Photo Frame
Digital Media
Player Personal Media
Retail Shopping Player
Terminal

9. Qt Is In Homes Today
Devices
–Roku Netflix Player
–Neuros OSD
–Blu-Ray Players
Software
–MythTV PVR
–LinuxMCE
9 © 2009 Nokia

10. Bring Internet Media into the Home
Internet Connected Web Streaming Infotainment Portals
“HD” Devices
INTERNET
HTTP
H.264
Flash
Etc.
10

11. Typical STB Software Architecture
3rd Party
OEM App
App
3rd Party Middleware
Qt WebKit
Browser
Toolkit
STB Adobe®
Qt GUI ToolKit Java VM
Middleware Flash Lite®
Qt for Embedded Linux
DRMs Audio Video Demux HDMI
CAs µCode µCode µCode Library Linux Kernel
MIPS MIPS Audio Video MIPS Peripheral
IPU Security CPU DSPs Decoders CPU I/O MIPS 74K

12. Agenda
• MIPS Introduction
• Emerging Trends
• Web Connectivity
• JIT Optimizations for WebKit
• Benchmarks
• Summary

13. What Drives Web Performance?
• Highly web content specific
– Interactive AJAX content vs Simple HTML
– Image heavy vs. text
• Page rendering
• Image rendering
• Javascript
• Interactive web content is heavily dependent on
Javascript performance
– PC: Chrome vs. IE8 vs. Firefox “performance” judged
mainly on Javascript engine performance

14. Faster Javascript Leads to “Faster” Web Experience
• PC browser performance differences directly
related to Javascript engine
– SquirrelFish Extreme (Nitro)
• Javascript Virtual Machine engine used in Webkit Open
Source Project
• Some projects that make use of Webkit:
Safari, Qt, Arora, Midori
– V8
• Chrome
– Tracemonkey (w/ nanoJIT)
• Firefox 3.5.x
– IE8

15. JIT and the Javascript Engine
• Developing a JIT speeds up browsing
performance on Javascript-based webpages
and applications using it as a scripting language
• JIT techniques also helpful for Tamarin
– Flash 10
– Yahoo Widgets
• Status:
– JIT completed and submitted to Webkit project for
review/acceptance
– MIPS incorporating into MIPS-Android HD
development

16. Agenda
• MIPS Introduction
• Emerging Trends
• Web connectivity
• JIT optimizations for WebKit
• Benchmarks
• Summary

17. MIPS JIT for WebKit JavaScriptCore
• Development environment: Debian 5.0 (lenny).
– Debian runs on top of Qemu simulators, MIPS Malta
boards (FPGA), or Sigma boards.
• Qt libraries are installed on Debian.
– # apt-get install libqt4-dev
• Webkit is configured and built with Qt (--qt) on
Debian.
• To accelerate compilation time, we copy Qt
libraries, Qt headers, Qt generated files, and
Makefile to an x86 Linux host.
Then, we use MIPS linux-cross toolchains from
CodeSourcery to cross-compile.

18. Implementing JIT
• JIT frameworks need to assign registers for
special purposes. The selection of registers is
important.
– Some registers are used for returned values.
– Some registers must be preserved across function
calls.
• The design for trampoline is important.
– We need to set up parameters in the stack to be
passed to functions.
– We need to support exceptions.
– For MIPS position-independent code, we need to
preserve the value of global-pointer register ($28) in
the trampoline code.

19. Implementing JIT (cont.)
• MIPS PC-relative branches cover 16-bit ranges.
– When branches are too far away, direct jump (J)
covers 26-bit ranges.
– LUI/ORI/JR covers 32-bit ranges.
• J and LUI/ORI/JR are not PC-relative instructions.
• When the buffer to hold instructions is moved, the target
of J and LUI/ORI/JR must be re-calculated and updated.
• The relaxation of branches need four extra words. A
short branch is created to jump over four extra words to
speed up.
• After JIT code is generated, we need to flush data cache
using synci (a user-level instruction).

20. All WebKit JIT optimizations are supported
• ENABLE_JIT
• ENABLE_JIT_OPTIMIZE_CALL
• ENABLE_JIT_OPTIMIZE_NATIVE_CALL
• ENABLE_JIT_OPTIMIZE_PROPERTY_ACCESS
• ENABLE_JIT_OPTIMIZE_METHOD_CALLS
• YARR_JIT

21. Agenda
• MIPS Introduction
• Emerging Trends
• Web Connectivity
• JIT Optimizations for WebKit
• Benchmarks
• Summary

22. Web Performance Benchmarks
Relative Javascript Benchmark Performance
Interpreted JIT
H/W Platforms:
74Kf = Sigma Designs SMP8642 @ 660 MHz
A8 = TI OMAP 3530 @ 500 MHz
Atom = Intel Atom 330 @ 1.6 GHz
>2x faster
than ARM
Same performance as
Atom @ a fraction
of the power and cost
74Kf_32K/32K_0KB 74Kf_32K/32K_256K (est) A8_16K/16K_256K Atom_32K/24K_512K
V8/Sunspider benchmark suite
All results normalized to 1 GHz

23. Agenda
• MIPS Introduction
• Emerging Trends
• Web Connectivity
• JIT Optimizations for WebKit
• Benchmarks
• Summary

24. Best Web and Multimedia Experience Driving Performance
2x performance of ARM!
Fraction of the cost and power consumption of Intel!