pdf-面向瘦客户端平台可重定向的全系统模拟器are

面向瘦客户端平台可重定向的全系统模拟器曲宁，赵雨来，管雪涛，程旭（北京大学微处理器研究开发中心，北京，100871北京大学计算机科学技术系，北京，100871）{quning,zhaoyulai,guanxuetao,chengxu}@mprc.pku.edu.cn摘要：高端嵌入式系统的硬件设计具有很强的多样性，其上的应用程序也跨越嵌入式和中低端桌面领域。瘦客户端系统是客户/服务器和浏览器/服务器环境中一种典型的高端嵌入式系统，能够整合本地和远程的计算资源。本文提出了面向瘦客户端系统而设计的Unichos全系统模拟器。针对嵌入式系统硬件平台多样化的特点，Unichos模拟器结合了可重定向的指令模板以及可扩展的设备模型，使其成为具有良好可重定向性的全系统模拟器。Unichos模拟器采用面向对象的方法对整个目标硬件系统建模，其上可以运行无修改的Linux2.4内核以及瘦客户端系统中所有应用程序。同时，Unichos模拟器能够灵活的支持不同粒度的性能模拟。最后本文通过两个实验案例进一步说明了Unichos模拟器在性能评测过程中的优势。关键词：计算机系统结构，瘦客户端，全系统模拟，可重定向，性能评测中图分类号:TP316文献标识码:AARetargetableFullSystemSimulatorforThinClientPlatformNingQu,YulaiZhao,XuetaoGuan,XuCheng(MicroprocessorResearchandDevelopmentCenter,PekingUniversity,Beijing,100871DepartmentofComputerScienceandTechnology,PekingUniversity,Beijing,100871){quning,zhaoyulai,guanxuetao,chengxu}@mprc.pku.edu.cnAbstract:Therearevarietiesofhardwaredesignsinhigh-endembeddedsystems,andtheapplicationsonitcoverembeddedareasandlow-enddesktopareas.Thinclientisatypicalhigh-embeddedsysteminclient/serverandbrowser/serverenvironment,whichcom-bineslocalandremotecomputingresources.ThispaperpresentsthedesignandimplementationofUnichos,afullsystemsimulatorforthinclientplatform.Unichosfocusesonretargetabilityformorearchitecturesofthinclientplatformsbycombiningtheretargetableinstructiontemplateandtheextensibledevicemodel.Unichosmodelsthecompletetargethardwaresysteminobject-orientedstructure,andsupportstheunmodifiedLinux2.4kernelandalloftheapplicationsforthinclient.Inaddition,Unichoscanflexiblyprovidesup-portforperformancesimulationindifferentlevelofdetail.Finally,weintroducetwocasestudiesbasedonUnichos,whichdemon-stratetheadvantagesofUnichosinperformanceevaluation.Keywords:computerarchitecture,thinclient,fullsystemsimulation,retargetability,performanceevaluation1.INTRODUCTIONTherearevarietiesofhardwaredesignsinhigh-endem-beddedsystems,andtheapplicationsonitcoverembeddedareasandlow-enddesktopareas.Thinclientisatypicalhigh-embeddedsysteminclient/serverandbrowser/serveren-vironment,whichcombineslocalandremotecomputingre-sources.Inaddition,applicationsonthinclientplatformrelyheavilyonthesupportofthenetworkandgraphicsdevicesandthesupportofoperatingsystem.TothoroughlystudyandanalysisthecharacterizationofapplicationsandOSonsuchkindofplatform,wedevelopanewfullsystemsimulator,Unichos,whichtargetsonthePKU-nitynetworkcomputer,ageneralthinclientbasedonPKUnitySoC(System-On-a-Chip).Unichosfocusesontheretargetabil-itybycombiningthecharacteristicsofretargetableinstructiontemplateinSimpleScalar[1][2]andextensibledevicemodelinBochs[3],whichmakeitsuitableformorekindsofthinclientplatforms.Sincethetypicalapplications(suchasbrowsersandremotedesktopgraphicsclient)spendasignificantportionofexecutiontimeintheoperatingsystem,Unichosmodelsthecompletetargethardwaresystemfaithfullytorunanunmodi-fiedLinux2.4onnetworkcomputer.Moreover,Unichossup-portsruntimesimulationstatusswitchingbetweenthefunc-tionalsimulationandperformancesimulationandruntimecon-figurationaccordingtodifferentsimulationrequirements.ThecompletesimulationandevaluationenvironmentprovidedbyUnichoshasbeenwidelyusedinthedevelopmentandresearchonthinclientplatformofPKUnitynetworkcomputer.Therestofthispaperisorganizedasfollows.Section2givesanoverviewoftherelatedworksonfullsystemsimula-tion.Section3detailsthedesignandimplementationofUnichos.Section4demonstratestheadvantagesofUnichosbyintroducingtwocasestudies.2.RELATEDWORKSSimpleScalar[1][2]toolkitprovidesseveralapplication-levelsimulators,whichmakeupofaretargetablehighperformanceevaluationplatformwidelyusedinsystemresearcharea.Sim-plescalar4.0providesss-os[1],afullsystemsimulatorforARMarchitecture,whichintegratesBochsdevicemodelintoSimplescalar.Tosomeextent,ss-osissimilartothedesignofUnichos;however,uptonowithasnotbeenreleasedyet.Asafullsystemsimulator,UnichosintegratesinstructiontemplateofSimpleScalarintoanobject-orienteddesign,whichhasthecharacteristicsofwell-definedabstractionandmodularity.Bochs[3]isafreeandcompletex86PCsimulator,whichcansupportmanydevicesinPCandcanrunpopularx86OSs.Bochs,however,hasnosupportforperformancesimulationandhaslimitationinsomeimportanthardwaresimulation.Forexample,itonlymodelsaNE2000EthernetcardwithoutDMAfunction.Incontrast,Unichossimulatesacompletemodernthinclient,PKUnitynetworkcomputer,andprovidesnecessarytiminginformationforperformancesimulation.SimOS[4][5]isoneoftheearliestfullsystemsimulatorsandplacesemphasesonsimulationperformance.However,SimOSdoesnotsupportgraphics.Itsnetworkimplementationreliesonaseparateproxyprocess,whichmayhavesideeffectsonnet-workperformancewhencommunicatingwiththeoutsideworld.LaterderivativesofSimOS,includingSimOS-Alpha,Si-mOS-PPC,Linux/SimOS[6]andPHARMsim[7],donotin-cludeatimingmodelforthenetwork.Inrecentfewyears,thereexistssomeotherwell-knownfullsystemsimulators,suchasSimics[8][9],M5[10]andetc.Simicssupportsmostofthemainstreamarchitecturesandsimulatesthefunctionforgraphicsandnetwork.Itprovidesuniformextensionmechanismtocreatecustomhardwaremod-els,whereasaddinganewISAsupportinSimicsisstillnon-trivi