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38 lines
1.1 KiB
Markdown
38 lines
1.1 KiB
Markdown
---
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title: "22-virtual-memory"
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aliases:
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tags:
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- cosc204
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- lecture
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---
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# Swapping and virtual memory
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swapping
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- if there is not enough physical memory we need to sawp processes out of the main ememory to the secondary storage e.g., disk
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- 
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- when a process is ready, it is swapped into the main memory
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- allows more processes to multitask
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partially loaded proceses
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- dynamic loading
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- load a potion of code when it is called as some code may not need to be executed, e.g., code for handling errors
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- pros
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- process not limited by amount of avilable memory
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- more processes multitasking
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- quicker to swap than entire process
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virtual memory
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- idea that processes dont need to be fully in memory to run
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extends main memory to secondary storage, and allows dynamic loading of processes while they execute
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- programmer deals with vmem just like paging scheme
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- mem manager in OS kernel controls loading pages of the process into main mem from secondary storage
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# Demand paging
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# page replacement algorithms
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# frame allocation
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# thrashing
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