TutorialGuide: TheSunflowerToolSuite HardwarePrototypesandSoftwareResearchPlatformsfor Failure-ProneandResource-ConstrainedEmbeddedSystems 1 2PhillipStanley-Marbell ,DianaMarculescu 1 TechnischeUniversiteitEindhoven, DenDolech2,Eindhoven5612AZ,TheNetherlands. %+3161-478-2010 2 DepartmentofECE,CarnegieMellon, 5000ForbesAve.,Pittsburgh,PA15213-3890, USA. Abstract. In computing systems research, software tools (notably, simu- lators) provide low-cost, flexible, and low turn-around time facilities for investigations, but abstract away many hardware details. Hardware im- plementations onthe otherhand, providetheultimateproofsofconcept, butrequirehardwaredesignexpertise,areusuallyexpensiveand inflexi- ble,andarenotalwaysdesignedtoexposeallpossiblesystemparameters to researchers. They are also rarely the subject of active evolution over timeasresearchplatformsintheirownright,assoftwaretoolsare. TheSunflowertoolsuiteisasuiteofhardwareplatformsandsimula- tion tools, intended to address these concerns. It comprises a full-system (embedded microarchitecture, networking, power, battery, device failure and analog signal modeling) simulator, a miniature energy-scavenging hardware platform, and a handheld computing device. The suite is in- tended to provide a set of complementary platforms for research in micro- and system-architectures for embedded systems, with emphases onenergy-efficiencyandfault-tolerance.Thistutorialwillprovidetheau- diencewithaworkingknowledgeofthedesign,implementationand us- ageofthecomponentsoftheSunflowertoolsuite. 1 TutorialObjectives The objectives of the tutorial are to provide a working knowledge of the use of the Sunflower full-system simulator, and Sunflower hardwareplatforms, to computingsystemsresearchers.Thetutorialcoverstwomaintopicareas: Ê Using and extending the Sunflower full-system simulator; the tutorial will detail the implementation of, and the facilities provided by, the Sun- flower framework for performing full-system simulation (microarchitec- ture, networking, power dissipation and supply, failure-modeling, and more,)ofnetworksofembeddedsystems. Ë Using the Sunflower hardware platforms; the simulation framework is complemented by open hardware platforms, and the tutorial will outline the process of using the hardware platforms in experimental evaluations andresearchdeployments.2 P.Stanley-Marbell,D.Marculescu 1.1 Intendedaudience Thetutorialistargetedatseveralpotentialaudiences: u Microarchitecture researchers, who are looking for a microarchitectural simulator for embedded systems that provides detailed models of the whole system that surrounds a processor or microcontroller. The tutorial willbeofparticularinteresttoresearchersinvestigatingsystemscontaining multiple(wiredorwirelessly)networkedprocessingelements,thoseinves- tigating the interaction of computation with input signals such as sensors, andresearchersinvestigatingtheeffectsofsoft-errors. u Sensor network researchers interested in investigating the computational aspectsoftheirprotocolsandsystemssoftware. u Systems researchers looking for a platform to enable them to develop compilers and operating systems for embedded systems, that has greater flexibility, transparencyand lower cost than hardware,but is also comple- mented/calibratedagainstactualavailablehardware. 1.2 Whatyoushouldexpecttogetoutofthistutorial Attheendofthisthreehourtutorial,itishopedthatyouwouldhavegained: u Theability to usethe Sunflowersimulation environment to modela single processoror networkedsystem ofembeddedprocessors,given anexisting systemconfiguration,andtointerpretthebehaviorofthemodeledsystem. u Theabilitytodefinenewsystemconfigurationsforsimulation,andtocom- pileC-languagebenchmarksforsimulationinSunflower. u A knowledge of the available resources for information on the simulation platform’sbuilt-infacilities,aswellasinformationoncustomizingthesim- ulatorviaruntimeorcompile-timeconfiguration,orsource-codemodifica- tion. u AnunderstandingofthebasicarchitectureoftheSunflowerhardwareplat- forms,andtheircapabilities. u The ability to request new features in the periodic revisions of the Sun- flowerhardwareplatforms. 2 Background There exist an abundance of tools for many aspects of computing systems research, from microarchitectural simulators that are the mainstay of com- puter architecture research [Augustetal.; Burgeretal., 1996], to networking simulators and other domain-specific tools. Academic research tools are sel- dom calibrated against specific hardwareplatforms during their development and evolution, and retrospective comparisons often yield interesting observa- Gibsonetal., 2000; Langendoen, 2006]. Even when the simulation plat-tions [ forms areindeedcalibratedagainsthardware,thereis seldomthe opportunityLED TutorialGuide: TheSunflowerToolSuite 3 to evolvethe hardwareplatformsinquestion. This is dueboth tothe expertise requiredfor implementing hardwaredesigns, as well asthe cost of fabrication of hardware prototypes. For high-performance computing systems research, the RAMP platform [Arvindetal., 2005] addresses many of these concerns, providinganopenplatformforresearchintomultiprocessorarchitectures.The goal of the Sunflower tool suite is to provide an actively evolving ecosystem of both hardware prototypes and simulation / analysis tools, for low-power embeddedsystems, withanemphasisontheinvestigation ofissuesrelatingto energy-efficiency, energy acquisition, fault-tolerance, and impact of hardware deploymentsontheenvironment. Failure Modeling Failure Modeling0 NetworkSignal Propagation Model Medium 1 Analog Sensors Data Transmission Model 1 Analog Microarchitecture signal 1 Simulation Network Interfaces2 Time-varying amplitude Network Power Estimation Power EstimationMedium 2Spatial attenuation model Voltage Regulator Model Analog NetworkAnalog 4 3 signal 2Medium 3signal 3 Battery Model Fig.1. IllustrativeexampleoftheSunflowerfull-systemsimulator’sorganization. On the side of simulation, the Sunflower full-system simula- tor [Stanley-MarbellandMarculescu, 2007b] (Figure 1) enables the evaluation of micro- and system-architectures for networked embedded systems, model- ingmanyaspectsofboththehardwareplatformsandtheenvironmentswithin whichtheyexecute. Top surface and size illustration: MicrophoneFlash Memory 2.7V SPI ADC GPIO, UART Microcontroller 1.8V Bottom surface:SRAM Flash Memory GPIO GPIO ADC Color Sensor Accelerometer 2.7V Fig.2. System architecture of the Sunflower sensor platform (left), and pictures of the currenthardwareprototype(right). UART0 UART2 Core CPLD I/O Temperature Sensor Voltage Regulator Energy-Scavenging Subsystem4 P.Stanley-Marbell,D.Marculescu The Sunflower sensor platform[Stanley-MarbellandMarculescu,2007a](Fig- ure2),isonephysicalrealizationofcomponentsmodeledwithintheSunflower full-systemsimulator,enablingthecalibrationandvalidationofsimulatorcon- figurationsagainstrealhardwareimplementations. Fig.3. The Sunflower mobile client platform has a 320×240 pixel color display (1), hu- midity/temperature(3),andpressuresensors(4),andadigitalcompass(6).Itincludesa dedicatedexpansionconnector(5),USB(7),andan802.15.4radiointerface(2),aswellas amicroSDslotforflash memoryor peripheralcards.Theprimarysourceofcomputing power is a 32-bit ARM7 implementation (AT91SAM7S256) with 64KB of on-chip RAM and 256KB of on-chip flash memory (on the rear side of the device), and the system is poweredbyathin2000mAhrechargeablelithiumpolymerbattery. 3, with its system architectureThe Sunflower mobile client platform (Figure shown inFigure4)isanothermemberofthesuiteofhardwaretools,andisin- tendedto beused,forexample,to studythehardwareandsoftwareaspectsof buildinglow-powermobilecomputing platformscontaining multipleprocess- ingelements. Additionalhardwareplatformswith complementaryhardwarecapabilities (e.g., wireless communication interfaces and graphical displays) are planned, anditisintendedtoemploytheseplatformsasaframeworkfortheimplemen- tation of ideas by a community of researchers who may not necessarily have interests or expertise in hardwaredesign, but might require specific hardware facilitiestoenabletheinvestigationofnovelsoftwarealgorithms. 1 2 3 4 5 6 7TutorialGuide: TheSunflowerToolSuite 5 320x240 pixel 18-bit color OLED display Input Device System Processor (Atmel AT91SAM7S ARM7) Sensors Atmospheric System Controller pressure (TI MSP430F2274) Display Controller Voltage Regulation, Gating, Humidity ... (TI MSP430F2370)& and Current Monitoring Temperature Rechargeable Battery 802.15.4 Digital Low- Radio Compass Power Real-Time RSSIUSB microSD Clock Interface between system controller and peripherals / sensors Power supply Fig.4. System architecture; The system controller implements the low-level software in- terfaces to peripherals and sensors, and applications run over the system processor, an ARMprocessorrunningFreeRTOS. 3 TutorialOutline Theplannedoutlineoftopicstobediscussedinthetutorialisasshownbelow: Topic Duration Motivationforthesuiteofhardwareandsimulationtools 5min Sunflowersimulatoroverview 5min Hands-onsimpleexampleandsetup:single-processorembeddedsystem 5min Microarchitecturesimulationanditsimplementation 5min Powerestimation,powersupply,andbatterymodelingimplementation 10min Modelinganalogsignalsexternaltoprocessor 10min Communicationinterconnectmodeling:wiredandwirelessnetworks 10min Largerexample:modelinganetworkofprocessors 10min Supportfordistributionsofrandomvariablesandconstants insimulation 5min RunningMiBench,ALPBench,SPECandotherbenchmarksonthesimulator 5min Break (30min) Sunflowerhardwareplatformsbriefoverview 10min Sunflowersensornodearchitecture 10min Sunflowerhandheld architecture 10min Hardwaretools 5min Compilationtools 5min UsingtheSunflowersimulatortoemulatetheSunflowerhardware 10min SubmittingrequestsforhardwarefeaturesintheperiodicHWrevisions 10min Summary,andpointerstofurtheravailableresources 5min Q&A 10min6 P.Stanley-Marbell,D.Marculescu 4 ContributorProfiles PhillipStanley-Marbellisapost-doctoralresearcherattheTechnischeUniver- siteitEindhoven.HereceivedthePhDincomputerengineeringfromCarnegie MellonUniversityin2007,andistheprincipalarchitectandimplementorofthe Sunflower simulation framework and hardware platforms. Prior to, and dur- inghisPhD,heheldindustrialpositionsatBell-Labs(LucentMicroelectronics), PhilipsConsumerCommunications,andNECresearchlabs.Hisresearchinter- estsincludeenergy-resourceconstrainedandfailure-pronesystems. Diana Marculescu received the Dipl. Eng. degree in computer science from UniversityPolitehnica ofBucharest,Romania,in 1991,andthePh.D.degreein computer engineering from the University of Southern California, Los Ange- les,in1998.SheiscurrentlyanAssociateProfessorofElectricalandComputer EngineeringatCarnegieMellonUniversity,Pittsburgh,PA.Herresearchinter- ests include energy-awarecomputing, CAD tools for low-power systems, and emerging technologies (such as electronic textiles or ambient intelligent sys- tems). Dr. Marculescu is the recipient of a National Science Foundation Fac- ulty Career Award (2000-2004),an ACM-SIGDA Technical Leadership Award (2003),andtheCarnegieInstituteofTechnologyGeorgeTallmanLaddResearch Award(2004).ShewasanIEEECircuitsandSystemsSocietyDistinguishedLec- turer(2004-2005)andistheChairoftheACMSpecialInterestGrouponDesign Automation(SIGDA). 5 ParticipantNotes This section is intended to help the participant organize any notes they may haveunderthedifferenttopicheadingscoveredduringthetutorial. 5.1 Motivationforthesuiteofhardwareandsimulationtools 5.2 SunflowerSimulatorOverviewTutorialGuide: TheSunflowerToolSuite 7 5.3 Hands-onsimpleexampleandsetup:single-processorembedded system 5.4 Microarchitecturesimulationanditsimplementation 5.5 Powerestimation,powersupply,andbatterymodelingimplementation 5.6 Modelinganalogsignalsexternaltoprocessor 5.7 Communicationinterconnectmodeling:wiredandwirelessnetworks 5.8 Largeexample:modelinganetworkofprocessors8 P.Stanley-Marbell,D.Marculescu 5.9 Support for distributionsof random variables and constants in simulation 5.10 RunningMiBench,ALPBench,SPECandotherbenchmarksonthe simulator 5.11 Break 5.12 Sunflowerhardwareplatformsbriefoverview 5.13 Sunflowersensornodearchitecture 5.14 SunflowerhandheldarchitectureTutorialGuide: TheSunflowerToolSuite 9 5.15 Hardwaretools 5.16 Compilationtools 5.17 UsingtheSunflowersimulatortoemulatetheSunflowerhardware 5.18 Submittingrequestsforhardwarefeaturesintheperiodichardware revisions 5.19 Summary,andpointerstofurtheravailableresources10 P.Stanley-Marbell,D.Marculescu