Transcription of Memory Management - School of Informatics
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Memory Management - School of Informatics
Operating SystemsMemory ManagementLecture 9 Michael O Boyle1 Memory Management Background Logical/Virtual Address Space vs Physical Address Space Swapping Contiguous Memory Allocation SegmentationGoals and Tools of Memory Management Allocate Memory resources among competing processes, maximizing Memory utilization and system throughput Provide isolation between processes Addressability and protection: orthogonal Convenient abstraction for programming and compilers, etc. Tools Base and limit registers Swapping Segmentation Paging, page tables and TLB (Next time) Virtual Memory : (Next next time)3 Background Program must be brought (from disk) into Memory and placed within a process for it to be run Main Memory and registers are only storage CPU can access directly Memory unit only sees a stream of addresses + read requests, or address + data and write requests Register access in one CPU clock (or less) Main Memory can take many cycles, causing a stall Cachesits between main Memory and CPU registers Protection of Memory required to ensure correct operationBase and Limit Registers A pair of baseandlimitregistersdefine the logical address space CPU must check every Memory access generated i
• Memory unit only sees a stream of addresses + read requests, or address + data and write requests • Register access in one CPU clock (or less) • Main memory can take many cycles, causing a stall • Cache sits between main memory and CPU registers • Protection of memory required to ensure correct operation
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