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?

What are placement and replacement algorithms, Placement algorithms :calcu...

Placement algorithms :calculate where in available real-memory to execute a program. Common functions are next-fit, first-fit, and best-fit. Replacement algorithms :are

Explain variable partitioning technique, VARIABLE PARTITIONING We can d...

VARIABLE PARTITIONING We can differ the partitions and change the location according to the size of the process. Here if a 10k process enters we are able to make a space of

BARBER SHOP PROBLEM, a) The barber shop has one barber, one barber chair, a...

a) The barber shop has one barber, one barber chair, and n chairs for waiting customers, to sit on. If there are no customers present, the barber sits down in the barber chair and

Explain secondary-storage management, What are the three main activities of...

What are the three main activities of an operating system in regard to secondary-storage management? a) Free-space management. b) Storage allocation. c) Disk scheduling.

Communications technique - application interaction protocols, Define the Co...

Define the Communications Techniques - Application interaction protocols    Communications techniques are well defined. They give developer the programmatic mechanism to transf

What is the basic function of assembler, Q. What is the basic function of A...

Q. What is the basic function of Assembler ? Input to an assembler is an assembly language program. Output is an object program and information which enables the loader to prep

Identify the binding and non-binding constraints, Crumbles Bakery needs to ...

Crumbles Bakery needs to decide how many and what types of cupcakes to make today. Currently, they make two types of cupcakes: chocolate cupcakes and carrot cake cupcakes. Chocolat

How can the deadlock be prevented-safe state, How can the deadlock be preve...

How can the deadlock be prevented-Safe State Safe state : A state is safe if the system is able to allocate resources to each process in some order and still avoid deadlock.

When page fault frequency in an operating system is reduced, When the Page ...

When the Page fault frequency in an operating system is reduced Locality of reference is appropriate to the process

Windows admin need it, Windows admin need it Project Description: We ...

Windows admin need it Project Description: We want to protect an executable on operating system level , so the process could be visible among all users while the executable r

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