Explain external fragmentation?, Operating System

Assignment Help:

Explain external fragmentation?

External fragmentation is the process where the free space and the space still available for use, in a piece of storage become separated into many small pieces. It is caused over time by de-allocating ("freeing") and allocating pieces of the storage space of many different sizes. The result is that, although one may perhaps have plenty of free space, it mayn't be able to all used, or at least used as effectively as one would like to.

For instance in a dynamic memory allocation a block of 1000 bytes might be requested but the largest contiguous block of free space or memory hole has only 300. Still if there are ten blocks of 300 bytes of free space separated by allocated regions one still cannot allocate the requested block of 1000 bytes.

External fragmentation also takes place in file systems as many files of different sizes are change size, created, and are deleted. The effect is even worse if a file which is separated into many small pieces is deleted, for the reason that this leaves similarly small regions of free space.

External fragmentation is able to be eliminated through a process called compaction, where existing objects are all moved in to one large adjacent block, keep left all of the remaining free space in one large block. Moving garbage collectors use compaction to enhance dynamic memory allocation performance and tools that defragment disk drives as well perform a compaction step. It is frequently possible to do a partial but still useful form of compaction more efficiently or to continually compact in an incremental fashion therefore that external fragmentation is always kept low.

 


Related Discussions:- Explain external fragmentation?

Structures for a file''s data, Q. Likewise some systems support many types ...

Q. Likewise some systems support many types of structures for a file's data while others simply support a stream of bytes. What are the merits in addition to demerits? Answer:

Define where a program generation activity aims, Define where a Program gen...

Define where a Program generation activity aims  Program generation activity aims at Automatic generation of program

Suggest a scheme for implementing this policy, Q. Consider a calculating e...

Q. Consider a calculating environment where a process is given the privilege of accessing object only n times. Suggest a scheme for implementing this policy. Answer: Add an i

What are the services provided by the operating systems, What are the servi...

What are the services provided by the operating systems?  Program Development It provides a variety of services and facilities, such as debuggers and editor, to help the

define system calls, When a computer is started on, the program that execu...

When a computer is started on, the program that executed first is named the ''operating system.'' It controls pretty much all applications in the computer. This adds who logs in, h

Explain objectives of the file management system, Problem: a) Define a ...

Problem: a) Define a ‘file' and list the objectives of the file management system. b) List the ways in which programs access files and determine for what file types you woul

Naming scheme for servers in an enterprise, Problem: Within a corporate...

Problem: Within a corporate environment, there are usually many servers located across various departments. Naming of servers is often a tedious task. In many circumstances, w

Keeping track of free memory, How do we keep track of where the free pieces...

How do we keep track of where the free pieces of memory are? One idea is to maintain a set of linked-lists of free space; each linked-list will store free chunks of some given size

Compute the effective instruction time on the system, Q. An operating syst...

Q. An operating system sustains a paged virtual memory using a central processor with a cycle time of 1 microsecond. It costs an additional one microsecond to access a page other

Define some language processors, Define Name of some language processors?  ...

Define Name of some language processors?   Name of some language processors are as follow: Assembler, Compiler and Interpreter

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd