Memory Management

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1、Chapter9:MemoryManagement
Background
Swapping
ContiguousAllocation
Paging
Segmentation
SegmentationwithPagingOperatingSystemConcepts9.1Silberschatz,GalvinandGagne2002Background
Programmustbebroughtintomemoryandplacedwithinaprocessforittoberun.
Inputqueue–collectionofprocessesonthediskthatare

2、waitingtobebroughtintomemorytoruntheprogram.
Userprogramsgothroughseveralstepsbeforebeingrun.OperatingSystemConcepts9.2Silberschatz,GalvinandGagne2002BindingofInstructionsandDatatoMemoryAddressbindingofinstructionsanddatatomemoryaddressescanhappenatthreedifferentstages.
Compiletime:Ifmemoryl

3、ocationknownapriori,absolutecodecanbegenerated;mustrecompilecodeifstartinglocationchanges.
Loadtime:Mustgeneraterelocatablecodeifmemorylocationisnotknownatcompiletime.
Executiontime:Bindingdelayeduntilruntimeiftheprocesscanbemovedduringitsexecutionfromonememorysegmenttoanother.Needhardwaresup

4、portforaddressmaps(e.g.,baseandlimitregisters).OperatingSystemConcepts9.3Silberschatz,GalvinandGagne2002MultistepProcessingofaUserProgramOperatingSystemConcepts9.4Silberschatz,GalvinandGagne2002Logicalvs.PhysicalAddressSpace
Theconceptofalogicaladdressspacethatisboundtoaseparatephysicaladdr

5、essspaceiscentraltopropermemorymanagement.✦Logicaladdress–generatedbytheCPU;alsoreferredtoasvirtualaddress.✦Physicaladdress–addressseenbythememoryunit.
Logicalandphysicaladdressesarethesameincompile-timeandload-timeaddress-bindingschemes;logical(virtual)andphysicaladdressesdifferinexecution-t

6、imeaddress-bindingscheme.OperatingSystemConcepts9.5Silberschatz,GalvinandGagne2002Memory-ManagementUnit(MMU)
Hardwaredevicethatmapsvirtualtophysicaladdress.
InMMUscheme,thevalueintherelocationregisterisaddedtoeveryaddressgeneratedbyauserprocessatthetimeitissenttomemory.
Theuserprogramdealswi

7、thlogicaladdresses;itneverseestherealphysicaladdresses.OperatingSystemConcepts9.6Silberschatz,GalvinandGagne2002DynamicrelocationusingarelocationregisterOperatingSystemConcepts9.7Silberschatz,GalvinandGagne2002DynamicLoading
Routineisnotloa