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 is banker''s algorithm, What is banker's algorithm? Banker's algor...

What is banker's algorithm? Banker's algorithm is a deadlock avoidance algorithm that is applicable to a resource-allocation system with multiple examples of each resource type

Information system can be divided into three task areas, From hardware pers...

From hardware perspective, every information system can be divided into three task areas Presentation, Application Logic and Data Storage. The R/3 Basis software is extremely s

Page-table lookups, How exactly is a page table used to look up an address?...

How exactly is a page table used to look up an address? The CPU has a page table base register (PTBR)which points to the base (entry 0) of the level-0 page table. Each process h

Recovery regarding the file system in windows 2000, Write short note on rec...

Write short note on recovery regarding the file system in Windows 2000. In many file systems a power breakdown at the wrong time can damage the file system data structures so s

Evaluate the physical address, Compare between the one and two-dimensional ...

Compare between the one and two-dimensional memory organizations in terms of the  memory structure,  advantages, and disadvantages.  Which approach would better support the needs o

What is belady anomaly, What is Belady's anomaly When plotting on a g...

What is Belady's anomaly When plotting on a graph the page faults versus the number of available frames. We notice that the number of faults for four frames is greater than th

Process execution priorities, Priority Scheduling leads to the risk of star...

Priority Scheduling leads to the risk of starvation: a process is ready, but never is given the processor. Some preemptive priority schedulers therefore reserve a fraction of the p

Control the access of the three global variables, Give a brief introduction...

Give a brief introduction about the operation of your program and show that you understand the idea behind threads and mutual exclusion variable. Why do we need to use mutual exclu

Virtual memory, How a virtual memory can be implemented? What are the benef...

How a virtual memory can be implemented? What are the benefits of using virtual memory?

Explain two level directory, Two Level Directory This kind of structure...

Two Level Directory This kind of structure overcomes the problems of assigning unique names to the files. Thus there need not be any confusion among users. In this kind of s

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