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?

Memory management, example of first fit best fit and worst fit

example of first fit best fit and worst fit

Advanced synchronization, Synchronization serves two purposes: 1) to ensure...

Synchronization serves two purposes: 1) to ensure safety for updates on shared data (e.g. to avoid races conditions), and 2) to coordinate and order actions taken by threads (e.g.

What do you mean by semaphore?, What do you mean by semaphore?  Semap...

What do you mean by semaphore?  Semaphore : A synchronization variable that acquires on positive integer values. Invented by the Dijkstra P (semaphore): an atomic proce

Explain the entry-sequenced file organization, Entry-sequenced file organiz...

Entry-sequenced file organization The records in an entry-sequenced file are store up in the order they are written into the file. New records are for all time appended to

Explain components of conflict phase of dispatch latency, Explain Component...

Explain Components of conflict phase of dispatch latency The conflict phase of dispatch latency has two components 1. Preemption of any process running in the kernel. 2.

Implementing group policies in a windows environment, Question: (a) As...

Question: (a) As a System administrator, elaborate on how you can manage computer accounts in Active Directory of Windows Server 2008? (b) Explain the following user p

State the advantage of multiprocessor system, State the advantage of multip...

State the advantage of multiprocessor system? The advantages of multiprocessor system are:- a)      Enhanced throughput. b)      Economy of scale. c)       Enhanced re

Bind a real-time thread to an lwp, Q. Suppose an operating system maps user...

Q. Suppose an operating system maps user-level threads to the kernel utilizing the many-to-many model where the mapping is done through the use of LWPs. In addition the system allo

Define the dosexit function used in the os/2, Define the DosExit Function u...

Define the DosExit Function used in the OS/2 DosExit(action, resultCode)  DosExit function is to be called when a thread or process is finished executing. If EXIT_THREAD 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