1 Architectural Musings Rethinking Computer Systems Architecture Christopher Vick [email protected] June 3, 2012.

1

Architectural MusingsRethinking Computer Systems Architecture

Christopher [email protected]

June 3, 2012

2

Vision Talk

Mobile computing and current technologies fundamentally change key parameters and constraints for computer system architecture

Vast new opportunities for research of great interest to and great relevance for industry

Introduction

3

Outline Computer System Architecture Then (Circa 1970)

Scarce Resources & Bottlenecks Optimizations

Now (Mobile Computing Platforms) Scarce Resources & Bottlenecks Optimizations?

Qualcomm Research Questions?

4

COMPUTER SYSTEM ARCHITECTURE

5

Computer System Architecture Hardware

The 5 classic components (Patterson & Hennessy) Input, Output, Memory, Datapath, Control

Software System Virtual Machine (Hypervisor, VM, or VMM) Operating System Compilers & Tools

Definitions The way components fit together The arrangement of the various devices in a complete computer

system or network The instruction set plus a model of the execution of the

instruction set (Amdahl et al)

Computer System Architecture The selection and combination of hardware and software

components to assemble an effective computer system

6

Combination

7

Effective An optimization problem

Many variables Selection of hardware/software components Selection of interfaces/interconnects

Many constraints Physical, sociological, technical & cost constraints

Scarce Resources and Bottlenecks Maximize utilization of scarce resources Minimize impact of bottlenecks

8

THEN(CIRCA 1970)

9

Scarce Resources CPU Cycles

CPUs expensive Slow clock rates

Memory Locations Random Access Memory expensive Address/Data paths into CPU expensive

Skilled Programmers Relatively new discipline Poor language and tools support

10

Bottlenecks Programmer Productivity

Software development slow and expensive Low level programming paradigms

Memory Latency RAM latency gated overall speed (~2-3 MHz) Small RAM backed by vastly slower storage

I/O Bandwidth Limited CPU connectivity Crude communication mechanisms

11

Optimizations Time Sharing

Effective sharing of limited resource

Virtual Memory Effective sharing, and backing with cheaper alternative

Hardware Improvements Smaller features provide more resource and faster clock Large Scale Integration Better signaling to improve bandwidth

High Level Programming Languages Broadens productive programmer community Abstracts away some hardware complexity

12

Examples Digital PDP 11

16-bit address space Orthogonal instruction set Memory mapped I/O Unix, DOS, many others

IBM System 370 24-bit address space Virtual Memory VMS, VM/370, DOS/VS Backward compatibility with System 360

13

NOW(MOBILE COMPUTING)

14

Scarce Resources Energy

Fixed Energy Budget for mobile devices Thermal issues at all scales Tradeoff between performance and energy Shrinks no longer significantly improving consumption

Memory Bandwidth Providing bandwidth is expensive Memory interconnect consumes significant energy

15

Bottlenecks Memory Latency

Increasing gap between CPU speed and DRAM latency Physical distance to DRAM devices a factor

Concurrency Shortage of programmers who can handle this Inadequate language/tools support

I/O Bandwidth/Latency Wireless bandwidth lower than wired Consumes large amounts of energy

16

Example HTC One

Processor: 1.5 GHz Dual Core Qualcomm MSM8960 OS: Android™ 4.0 (ICS) Memory RAM: 1 GB DDR2 Memory Storage: 16 GB onboard storage Display: 4.7" HD super LCD 1280 x 720 Network: LTE CAT3 - DL 100 /UL 50 LTE: 700/AWS

WCDMA: 2100/1900/AWS/850 EDGE: 850/900/1800/1900

Battery: 1800 mAh Camera (Main): 8 MP, f/2.0, BSI, 1080p HD Video

(Front): 1.3 MP with 720p video Dimensions: 134.8 x 69.9 x 8.9mm

This is a General Purpose Computer!

17

Optimizations? Multi-core

Aggressive addition of cores and threads Hardware concurrency outstripping software New Concurrent Programming Models/Tools?

Memory Subsystem Significant contributor to total energy consumption Adding bandwidth is expensive New technologies addressing some energy issues

Wireless bandwidth enhancements (LTE Advanced,etc.)

Solutions from desktop/server or embedded worlds may not directly apply in mobile space!

18

Memory System Energy Retaining data (one second)

DRAM: ~1-10 pJ/bit self-refresh SRAM: 1200+ pJ/bit, and rising over time [ITRS 2009]

4 pJ/bit (45nm LP, standby) [Barasinski et al., ESSCIRC ‘08] Flash, PCM, STT RAM…: Zero !

Moving Data 32-bit value:

Recompute: 60 pJ (Razor) Send 1mm: 10 pJ Retain in cache for 1 ms: 38 pJ Retain in DRAM for 1 second: 32+ pJ

19

Move less! Caches physically close to CPU Locality, locality, locality (the first rule of chip real estate)

Retain less! Power off unused caches lines [Kaxiras et al., ISCA ‘01] “Drowsy” caches [Flautner et al., ISCA ‘02] … with compiler analysis

[Zhang et al., Trans. Emb. Comp. Sys. 4(3) 2005] Don’t refresh unused DRAM … e.g. with garbage collection [Chen et al., CODES+ISSS ‘03]

Reducing Memory System Energy

20

Maintaining the illusion of a single flat memory address space is too expensive On-chip caches can be major consumers of area and energy Coherence protocols are expensive and difficult to scale

• Alternative: software-managed memory hierarchies– Tightly-coupled memory (TCM), scratchpads

– Do not require tag memory, address comparison logic

– More area- and energy-efficient

– Help bridge gap between bandwidth and throughput

Extending the Memory Model

21

Different programming paradigm: software explicitly orchestrates all transfers between on-chip and off-chip memory areas

Major implications on memory management Scratchpad allocation strategies Data partitioning strategies Dynamic relocation between scratchpad and DRAM to track the

program’s locality characteristics

Opportunities for compile-time and runtime optimization

Challenges in both Hardware and Software!

New Challenges and Opportunities

Qualcomm ResearchExcellence in Wireless

MAY | 2012 WWW.QUALCOMM.COM/RESEARCH

2323

State of the Art Capabilities Fostering Innovation

• Prototype Development Facilities

• CPU Simulation Clusters

• Antenna Ranges

• Outdoor Field Systems

• 30% of engineers with PhD, 50% Masters

• Systems, HW, SW, Standards, Test Engineering

• Ventures, Bus Dev, Technical Marketing, Program Mgmt.

Complete Development LabsHuman Resources

24

Global Research and Development Organization

UNITED STATES EUROPE ASIA

• San Diego, CA

• Santa Clara, CA

• Bridgewater, NJ

• Cambridge, UK

• Nuremberg, Germany

• Vienna, Austria

• Beijing, China

• Bangalore and Hyderabad, India

• Seoul, S. Korea

25

Qualcomm Research & University RelationsACADEMIC COLLABORATION TO FOSTER ADVANCED RESEARCH

RESEARCH

Ongoing relations with more than 30 US and 25 International Universities Current funding includes MIT, UC Berkeley, Stanford,  UCSD, UT Austin, ASU,

UIUC, Univ. of Michigan, EPFL, IISc Bangalore, KAIST, Tsinghua

Research collaboration spans variety of technical areas Computer vision, multicore processing, context aware computing, machine

learning,  low power devices,, wireless networks and signal processing, etc..

Qualcomm Innovation Fellowship (QInF) invests on innovative ideas Close interactions between Qualcomm Research engineers, graduate students and

professors

26

INNOVATEBEYOND WAN

Wireless Local Area

EXCELLING IN ALL FORMS OF WIRELESS

TAKE WWAN TO THE NEXT LEVEL

IMPROVING WWAN TECHNOLOGY

Processors & Devices

RE-ARCHITECTING NEXT-GEN MOBILE

DEVICES

BREAKTHROUGH PERFORMANCE

Application Enablers

TRANSFORMING THE MOBILE USER

EXPERIENCE

ENABLE SMART APPLICATIONS

Qualcomm Research For The Wireless Future

3G/4G

27

Innovate Beyond WANWIRELESS LOCAL AREA

PEANUT WIFI ADVANCED LTE D2D (FLASHLINQ) INNAV

• Next gen short range ultra-low power radio

• Multi Gbps WLAN using 5 GHz and 60 GHz band.

• Next Gen low-power WiFi for Internet of Things

• Proximal Wireless

• First Gen device-to-device wireless network

• Autonomous discovery

• Direct communications

• Indoor positioning for indoor location based applications

• Map tools for Mobile Devices

28

AUGMENTED REALITY LOOK LISTEN DASH AWARE

• Mobile user interface

• Computer vision for mobile devices

• Multiple language text detection and recognition

• With Mobile phone camera view finder

• Background Audio processing

• Augmented user experience

• Efficient video delivery over HTTP for mobile devices

• Build awareness in mobile devices

• For enhanced daily life situations

Enable Smart ApplicationsELEVATE THE WIRELESS USER EXPERIENCE

29

Breakthrough Device PerformanceRE-ARCHITECTING NEX-GEN DEVICES

ADVANCED RADIO TECHNOLOGIES MANTICORE GRYPHON

• New RF front-end and baseband technologies

• RF/antenna and systems/protocol techniques

• Concurrent multi-radio operation

• Advanced mobile device SW platforms

• Improved user experience

• Virtual machine design for SoC architecture

• Enabling higher power efficiency

Thank You