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?

Basic synchronization, (Add synchronization to your solutions to HW 3 to el...

(Add synchronization to your solutions to HW 3 to eliminate all of the race conditions.  You should not remove any of the sleep() commands that you used to produce the race conditi

Explain about time sharing systems, Q. Explain about Time Sharing Systems? ...

Q. Explain about Time Sharing Systems? Time Sharing Systems Multi-programmed batched systems provide an environment where various system resources (for illustration CP

Why is rotational latency is not taken in disk scheduling, Why is rotationa...

Why is rotational latency usually not considered in disk scheduling? How would you modify SSTF, SCAN, and C-SCAN to include latency optimization? Most disks do not export their

Shell scripting, A friend has promised to log in at a particular time. Howe...

A friend has promised to log in at a particular time. However, he needs to be contacted as soon as he logs in. The shell script checks after every minute whether he has logged in o

Parent process: why not finishing and how to make finish, #include #inclu...

#include #include #include #include #include int main(void) { int pchan[2], pid, rval, cvar; char buf[20]; if (pipe(pchan) == -1){

How resolution of externally defined symbols is performed, Resolution of ex...

Resolution of externally defined symbols is carried out by    Resolution of externally defined symbols is carried out by Linker

Why is it significant to balance file system I/O among disks, Q. Why is it ...

Q. Why is it significant to balance file system I/O among the disks as well as controllers on a system in a multitasking environment? Answer: A system can perform mere

Scheduler that select process from secondary storage device, A scheduler th...

A scheduler that selects processes from secondary storage device is known as                    Medium term scheduler is a scheduler that selects processes from secondary stor

System protection, what is the need-to-know principle? why is it important ...

what is the need-to-know principle? why is it important for a protection system to adhere to this principle?

Determine the value to be loaded in relocation register, Refer a program wi...

Refer a program with a linked origin of 5000. Suppose the memory area allocated to it have the start address of 70000. Determine the value to be loaded in relocation register?

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