OS_ch08_F07 - I.-C. Lin, Assistant Professor. Textbook:...

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I.-C. Lin, Assistant Professor. Textbook: Operating System Principles 7ed CHAPTER 8: MEMORY MANAGEMENT
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hapter 8: Memory Management Chapter 8: ackground ± Background ± Swapping ± Contiguous Memory Allocation ging ± Paging ± Structure of the Page Table ± Segmentation ± Example: The Intel Pentium
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ackground Background rogram m st be bro ght into memor and placed within a ± Program must be brought into memory and placed within a process for it to be run ± Input queue collection of processes on the disk that are aiting to be brought into memory to run the program waiting to be brought into memory to run the program ser programs go through several steps before being run ± User programs go through several steps before being run
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inding of Instructions and Data to Memory Binding of Instructions and Data to Memory ddress binding of instructions and data to memory addresses can ± Address binding of instructions and data to memory addresses can happen at three different stages ompile time ± Compile time : ² If memory location known a priori, absolute code can be generated; must recompile code if starting location changes ± Load time : ² Must generate relocatable code if memory location is not known at compile time ± Execution time : ² Binding delayed until run time if the process can be moved during its execution from one memory segment to another. Need hardware support for address maps (e.g., base and limit registers ).
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ultistep Processing of a User Program Multistep Processing of a User Program
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gical vs. Physical Address Space Logical vs. Physical Address Space e concept of a logical ddress space at is bound to a separate ± The concept of a logical address space that is bound to a separate physical address space is central to proper memory management ± Logical address generated by the CPU; also referred to as virtual address g gy ; ± Physical address address seen by the memory unit ± Logical and physical addresses are the same in compile-time and load-time address-binding schemes. ± Logical (virtual) and physical addresses differ in execution-time address-binding scheme
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emory- anagement Unit ( MU Memory Management Unit ( MMU ) ardware device that maps virtual to physical address ± Hardware device that maps virtual to physical address MMU scheme the value in the relocation register is added to ± In MMU scheme, the value in the relocation register is added to every address generated by a user process at the time it is sent to memory ± The user program deals with logical addresses; it never sees the real physical addresses
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Dynamic relocation using a relocation register
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ynamic Loading Dynamic Loading routine not loaded until it is called ± A routine is not loaded until it is called t t tili ti d ti i ± Better memory-space utilization; unused routine is never loaded ± Useful when large amounts of code are needed to handle frequently occurring cases infrequently occurring cases o special support from the operating system is required ± No special support from the operating system is required ± Implemented through program design
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OS_ch08_F07 - I.-C. Lin, Assistant Professor. Textbook:...

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