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?

Which of the subsequent instructions should be privileged, Q. Which of the ...

Q. Which of the subsequent instructions should be privileged? a) Read the clock b) Clear memory c) Set value of timer d) Issue a trap instruction e) Turn off interr

Explainoptimal page replacement in detail, Optimal page replacement An...

Optimal page replacement An optimal page replacement algorithm has the least page fault rate of all algorithms. The algorithm states that put back the page that will not be us

Logic gates, Determine the equation for the y and truth table for the circu...

Determine the equation for the y and truth table for the circuits

Identifying parallelism, Identifying parallelism A formal way to identi...

Identifying parallelism A formal way to identify parallelism in an activity is to draw a task dependence graph in a directed graph in which each vertex represents a task to

Explain memory management using link lists, MEMORY MANAGEMENT USING LINK LI...

MEMORY MANAGEMENT USING LINK LISTS The first one is for showing it is process or hole, second is for starting address and third is for length of the process and last is a point

Android, Which android version is available till now

Which android version is available till now

Why do systems stay track of the type of a file, Q. Why do some systems sta...

Q. Why do some systems stay track of the type of a file while others leave it to the user or simply don't implement multiple file types? Which system is "better?" Answer: A f

necessary conditions for a deadlock , Q) a. Given that the first three nec...

Q) a. Given that the first three necessary conditions for a deadlock are in place, comment on the feasibility of the following strategy. All processes are given  unique priorities.

How does user specify block to be fetched in direct access, How does user s...

How does user specify block to be fetched in direct access? By specifying the relative block number, relative to first block in file, which is block 0.

Define rotational latency and disk bandwidth, Define rotational latency and...

Define rotational latency and disk bandwidth. Rotational latency is the additional time waiting for the disk to rotate the wanted sector to the disk head. The disk bandwidth is

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