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中科大操作系统原理与实现课件8_memory1.pdf

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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 background Storagehierarchy Memoryprotection Programexecution,loading&linking ContiguousMemoryAllocation Swapping Swapping(对换) ...... Background IStoragehierarchy Imemoryprotection IProgramexecution,loading&linking ...... Outline background Storagehierarchy Memoryprotection Programexecution,loading&linking ContiguousMemoryAllocation Swapping Swapping(对换) ...... StoragehierarchyI I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 Storagehierarchy IStoragesystemsinacomputer systemcanbeorganizedina hierarchy ISpeed,accesstime ICostperbit IVolatility ...... MemoryVS.register ISame:AccessdirectlyforCPU IRegistername IMemoryaddress IDifferent:accessspeed IRegister,onecycleoftheCPUclock IMemory,Manycycles(2ormore) IDisadvantage: ICPUneedstostallfrequently&thisisintolerable IRemedy Icache ...... Caching ICaching(高速缓存技术） ICopyinginformationintofasterstoragesystem IWhenaccessing,firstcheckinthecache, IifIn:useitdirectly INotin:getfromupperstoragesystem,andleaveacopyin thecache IUsingofcaching IRegistersprovideahigh-speedcacheformainmemory IInstructioncache&datacache IMainmemorycanbeviewedasafastcacheforsecondary storage I… ...... Outline background Storagehierarchy Memoryprotection Programexecution,loading&linking ContiguousMemoryAllocation Swapping Swapping(对换) ...... Memoryprotection IBaseregisterprotectionscheme IBaseregister＋Limitregister IMemoryoutsideisprotected IOShasunrestrictedaccesstoboth monitoranduser’smemory ILoadinstructionsforthebase/limit registersareprivileged ...... Outline background Storagehierarchy Memoryprotection Programexecution,loading&linking ContiguousMemoryAllocation Swapping Swapping(对换) ...... Programexecution,loading&linkingI IVonNeumannarchitecture(冯·诺依曼体系结构) IProgrammustbebroughtintomemory IMainmemoryisusuallytoosmall ...... Programexecution,loading&linkingII IProgrammustbeplacedwithin ap