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操作系统原理与设计第8章MainMemory1陈香兰中国科学技术大学计算机学院2009年11月......提纲backgroundStoragehierarchyMemoryprotectionProgramexecution,loading&linkingContiguousMemoryAllocationSwappingSwapping(对换)......BackgroundIStoragehierarchyImemoryprotectionIProgramexecution,loading&linking......OutlinebackgroundStoragehierarchyMemoryprotectionProgramexecution,loading&linkingContiguousMemoryAllocationSwappingSwapping(对换)......StoragehierarchyII存储器是计算机系统的重要组成部分I容量、价格和速度之间的矛盾I内存、外存；易失性和永久性I内存，是稀缺资源I在现代计算机系统中，存储通常采用层次结构来组织StoragehierarchyIStoragesystemsinacomputersystemcanbeorganizedinahierarchyISpeed,accesstimeICostperbitIVolatility......MemoryVS.registerISame:AccessdirectlyforCPUIRegisternameIMemoryaddressIDiﬀerent:accessspeedIRegister,onecycleoftheCPUclockIMemory,Manycycles(2ormore)IDisadvantage:ICPUneedstostallfrequently&thisisintolerableIRemedyIcache......CachingICaching(高速缓存技术）ICopyinginformationintofasterstoragesystemIWhenaccessing,ﬁrstcheckinthecache,IifIn:useitdirectlyINotin:getfromupperstoragesystem,andleaveacopyinthecacheIUsingofcachingIRegistersprovideahigh-speedcacheformainmemoryIInstructioncache&datacacheIMainmemorycanbeviewedasafastcacheforsecondarystorageI…......OutlinebackgroundStoragehierarchyMemoryprotectionProgramexecution,loading&linkingContiguousMemoryAllocationSwappingSwapping(对换)......MemoryprotectionIBaseregisterprotectionschemeIBaseregister＋LimitregisterIMemoryoutsideisprotectedIOShasunrestrictedaccesstobothmonitoranduser’smemoryILoadinstructionsforthebase/limitregistersareprivileged......OutlinebackgroundStoragehierarchyMemoryprotectionProgramexecution,loading&linkingContiguousMemoryAllocationSwappingSwapping(对换)......Programexecution,loading&linkingIIVonNeumannarchitecture(冯·诺依曼体系结构)IProgrammustbebroughtintomemoryIMainmemoryisusuallytoosmall......Programexecution,loading&linkingIIIProgrammustbeplacedwithinap