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?

Define the throughput of a system, Define the “Throughput” of a system  ...

Define the “Throughput” of a system  Throughput is Number of programs processed by it per unit time

Define paging , Paging: Only the needed memory pages are moved to main me...

Paging: Only the needed memory pages are moved to main memory from the swap machine for execution. Process size does not matter. Produce the concept of the virtual memory. It

Describe internal layout of the file system in windows 2000, Describe the i...

Describe the internal layout of the file system in windows 2000. The basic entity in NTFS is a volume and a volume is created by the Windows 2000 disk administrator utility and

Dynamically loadable kernel modules, Q. Dynamically loadable kernel module...

Q. Dynamically loadable kernel modules give elasticity when drivers are added to a system however do they have disadvantages too? Under what situations would a kernel be compiled

Compute how many disk input - output operations are required, Q. Consider ...

Q. Consider a file at present consisting of 100 blocks. Presume that the file control block (and the index block in the case of indexed allocation) is already in memory. Compute h

Linux kernel components, Example 1.  The diagram illustrating the data stru...

Example 1.  The diagram illustrating the data structures of in-memory VFS objects and on-disk objects and their relationships on slide 24 of the lecture notes OSD.4. This diagram i

Explain two-phase locking protocol, Q. Show that a few schedules are possib...

Q. Show that a few schedules are possible under the two-phase locking protocol however not possible under the timestamp protocol and vice versa. Answer: A schedule that is auth

Explain threads in details?, What are threads? A thread - sometimes c...

What are threads? A thread - sometimes called as an implementation context or a lightweight process - is a single sequential flow of control within a program. We use threads

Can a direct access file be read sequentially, Can a direct access file be ...

Can a direct access file be read sequentially? Explain. Yes. Keep a counter, cp, initially set to 0. After reading record cp, increment cp.

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