Virtual_memory - Chapter 6 Virtual Memory Dhamdhere:...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 1 Copyright 2005 Virtual Memory Chapter 6 Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 2 Copyright 2005 Virtual memory Virtual memory is an illusion of memory that is larger than the real memory It is implemented using noncontiguous memory allocation * The memory management unit (MMU) performs address translation. (It is called the address translation unit (ATU) in this set of slides. Only some parts of a process are loaded in memory; other parts are stored on disk and loaded only when needed The virtual memory handler ( VM handler ) is that part of the kernel which manages virtual memory. Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 3 Copyright 2005 Overview of virtual memory Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 4 Copyright 2005 Logical address space, physical address space and address translation Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 5 Copyright 2005 Address translation in a paged virtual memory system Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 6 Copyright 2005 Fields in a page table entry Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 7 Copyright 2005 Steps in address translation Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 8 Copyright 2005 Effective memory access time Effective memory access time @ = h x 2 x access time of memory + (1 h ) (access time of memory + Time required to load the page + 2 x access time of memory) where h is the hit ratio in memory, i.e., the probability that the page containing a logical address referenced by a process is already in memory @ : The page table itself exists in memory Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 9 Copyright 2005 Demand loading of pages Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 10 Copyright 2005 Ensuring good system performance When a page fault arises in the currently executing process, the kernel switches to another process The page whose reference led to the page fault is loaded in memory Operation of the process that gave rise to the page fault is resumed sometime after the required page has been loaded in memory Chapter 6 Virtual Memory Dhamdhere: Operating Systems A Concept-Based Approach Slide No: 11 Copyright 2005 Performance of virtual memory Performance of virtual memory depends on the hit ratio in memory High values of the hit ratio are possible due to the principle of locality of reference It states that the next logical address referenced by a process is likely to be in proximity of the previous few logical addresses...
View Full Document

This note was uploaded on 11/15/2010 for the course ECE 1234 taught by Professor G.wdwdw during the Spring '10 term at St. Johns Seminary.

Page1 / 55

Virtual_memory - Chapter 6 Virtual Memory Dhamdhere:...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online