Not yet registered? Create a OverBlog!

Create my blog

All about virtual memory

In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualises a computer architecture's various forms of computer data storage, such as Random Access Memory and disk storage, thus allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which behaves like directly addressable read/write memory. (RAM) . Read this article to learn more about virtual memory.

History

Virtual memory was introduced to the x86 architecture with the protected mode of the Intel 80286 processor, but its segment swapping technique scaled poorly to larger segment sizes. The Intel 80386 introduced paging support underneath the existing segmentation layer, enabling the page fault exception to chain with other exceptions without double fault. However, loading segment descriptors was an expensive operation, causing operating system designers to rely strictly on paging rather than a combination of paging and segmentation.

Page tables

Page tables are used to translate the virtual addresses seen by the application into physical addresses used by the hardware to process instructions. Such hardware that handles this specific translation is often known as the memory management unit. Each entry in the page table holds a flag, indicating whether the corresponding page is in real memory or not. If it is in real memory, the page table entry will contain the real memory address at which the page is stored. When a reference is made to a page by the hardware, if the page table entry for the page indicates that it is not currently in real memory, the hardware raises a page fault exception, invoking the paging supervisor component of the operating system.

Paging supervisor

This part of the Operating System creates and manages page tables. If the hardware raises a page fault exception, the paging supervisor accesses secondary storage, returns the page that has the virtual address that resulted in the page fault, updates the page tables to reflect the physical location of the virtual address and tells the translation mechanism to restart the request. When all physical memory is already in use, the paging supervisor must free a page in primary storage to hold the swapped-in page. The supervisor uses one of a variety of page replacement algorithms, such as least recently used to determine which page to free

Same category articles Digital & online

The benefits of media planning software

The benefits of media planning software

In the past, media planners did not have access to media planning software. however, as technology improved advertising agency software became more and more popular. there are many benefits to using this type of software in the advertising world. people who create good media plans will save both time and money. this article highlights the benefits of media planning software.
The Mandarin Translation network: The facts

The mandarin translation network: the facts

Learning chinese mandarin has become very popular in recent years. to this end, there exist numerous mandarin online translation services that can assist you in the process. nonetheless, should you be looking for some professional document translations, then some translate online networks will carry out the task for you, ensuring your documents retain the accuracy and quality of the original. here follow some facts on the specialist mandarin translation network.
How to use spss?

How to use spss?

Considered as a complete and comprehensive system for data analysis, spss is being used as a computer program that is able to survey authoring and deployment i.e. ibm spss data collection. an important feature in spss is that it can take any type of file and use the same to provide tabulate reports, charts, plots, and trends, etc.
How to buy images from picture hosting sites

How to buy images from picture hosting sites

Be it for professional or private use, sometimes your own collection of photographs might not have the image that you require for a project that you are currently working on. whilst there are many millions of images available online, thought has to be taken into consideration before using one these in your work, mainly through potential copyright reasons that may crop up. this article will guide you through buying images from picture hosting sites.