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Table of contents
1.
Introduction
2.
What is Fragmentation in Operating System?
3.
Causes of Fragmentation
4.
Types of Fragmentation in OS
4.1.
1. Internal Fragmentation
4.2.
2. External Fragmentation
5.
Implications of Fragmentation: Why It Matters
6.
Role of Fragmentation in Operating System
7.
Fragmentation Prevention Techniques
7.1.
1. Compaction
7.2.
2. Paging and Segmentation
8.
Advantages of Fragmentation
9.
Disadvantages of Fragmentation
10.
Frequently Asked Questions
10.1.
What is fragmentation in operating system?
10.2.
What are the 4 types of fragmentation?
10.3.
What is internal and external fragmentation?
10.4.
How to avoid fragmentation in OS?
10.5.
What is the difference between fragmentation and segmentation?
11.
Conclusion
Last Updated: May 9, 2024
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Fragmentation in OS

Author Rashmi
0 upvote
Roadmap to SDE career at Amazon
Speaker
Anubhav Sinha
SDE-2 @
25 Jun, 2024 @ 01:30 PM

Introduction

Fragmentation in operating systems is a fundamental concept intricately tied to memory management. Understanding it is crucial for Operating System efficiency and by extension, overall system performance.

Fragmentation in OS

This article explores the meaning of fragmentation, its types, causes, impacts, and possible solutions, accompanied by a FAQ section for clarity.

What is Fragmentation in Operating System?

Fragmentation is an unwanted issue that occurs in an operating system in which a process is unloaded and loaded from memory, causing the free memory space to become fragmented. As a result, the process can not be assigned to the memory blocks due to their small size.

In the realm of operating systems, fragmentation is a phenomenon that impacts storage space efficiency, impeding both capacity and performance. Fragmentation usually arises when blocks of storage space are scattered, leading to potential wastage.

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Causes of Fragmentation

At its core, fragmentation is caused by the dynamic allocation and deallocation of memory during a program's execution. External fragmentation occurs when a process is removed from memory, leaving a 'hole' of unused memory. If the hole is too small or poorly located to accommodate subsequent processes, fragmentation occurs.

Internal fragmentation, on the other hand, results from allocating memory in fixed block sizes. If a process does not fully utilize its allocated block, the remaining memory is wasted. This is essentially space reserved for a specific process but left unused, creating inefficiency within the system.

Types of Fragmentation in OS

Fragmentation is a condition in which memory is allocated but not used efficiently. Below are the most common fragmentations:

1. Internal Fragmentation

Contrastingly, internal fragmentation occurs when memory blocks allocated to processes exceed what they initially requested. The leftover space within a block, which remains unused, gives rise to internal fragmentation.

For Example,

Internal Fragmentation

Internal fragmentation is a classic case of over-allocation, where system resources are wasted within allocated blocks. While attempts to prevent under-allocation and the associated performance issues are well-intentioned, overcompensation can lead to its own set of problems.

Consider this simple representation of internal fragmentation:

ProcessMemory RequestedMemory Allocated
P110 units15 units
P220 units25 units
P330 units35 units

Here, each process is allocated more memory than it requested, leading to wasted space and internal fragmentation.

2. External Fragmentation

External fragmentation arises when free memory blocks in a system become separated and non-contiguous. This typically happens when memory blocks, once allocated, are freed up, leading to 'holes' of unused memory spread across the system.

External Fragmentation

The issue is that these 'holes' or blocks may not be large enough to satisfy subsequent allocation requests, despite collectively having sufficient space. Consequently, the system is unable to use this memory effectively, leading to wasted resources and decreased efficiency.

Consider this simple representation of external fragmentation:

Memory BlocksState
Block 1Used
Block 2Free
Block 3Used
Block 4Free
Block 5Used

Here, although there is free memory (Blocks 2 and 4), it is not contiguous, resulting in external fragmentation.

Also see, Difference Between Bit and Byte

Implications of Fragmentation: Why It Matters

Fragmentation can significantly impact the performance of a system. It can lead to inefficient use of memory, increased time complexity in allocation and deallocation operations, and overall sluggishness in system performance. Severe fragmentation may also cause allocation requests to fail, resulting in program crashes or slowdowns.

Moreover, as fragmentation increases, the overhead of managing memory increases as well. The system spends more time and resources organizing and keeping track of memory blocks, which detracts from other tasks and overall system performance.

Role of Fragmentation in Operating System

Fragmentation in an operating system refers to the phenomenon where storage space becomes divided into smaller, non-contiguous segments over time. This fragmentation can occur in both memory (RAM) and disk storage. Here's how fragmentation impacts operating systems:

  • Memory Fragmentation: In memory, fragmentation can lead to inefficient memory usage. External fragmentation occurs when free memory is broken into small, non-contiguous blocks, making it challenging to allocate larger chunks of memory to processes even if sufficient total memory is available. This can result in wasted memory and reduced system performance.
  • Disk Fragmentation: Disk fragmentation occurs when files are stored in non-contiguous clusters on a disk. Over time, as files are created, modified, and deleted, the disk space becomes fragmented, with parts of files scattered across the disk. This can slow down file access times since the disk head must move more frequently to access all parts of a file.
  • Impact on Performance: Fragmentation can degrade system performance by increasing disk seek times, memory allocation overhead, and overall system response time. As fragmentation worsens, the system may experience slowdowns and decreased efficiency, impacting user experience and productivity.
  • Defragmentation: To mitigate fragmentation, operating systems often provide defragmentation tools that rearrange disk data or memory blocks to consolidate free space and reduce fragmentation. Defragmentation helps improve disk and memory performance by optimizing data placement and reducing seek times.

Fragmentation Prevention Techniques

Some fragmentation prevention techniques are:-

1. Compaction

Compaction aims to overcome external fragmentation by moving all free memory areas together. It involves relocating existing processes so that they are contiguous and all of the free memory is together in one block. Although compaction effectively solves external fragmentation, it requires significant CPU resources, which might impact the system's performance.

2. Paging and Segmentation

Paging is another technique for combating external fragmentation. The memory is divided into fixed-sized blocks known as pages. When a process needs to be loaded into memory, it's divided into pages of the same size. These pages can be loaded into any available memory frames, thus preventing external fragmentation.

Segmentation, on the other hand, is designed to prevent internal fragmentation by providing a dynamic and flexible solution to memory management. Memory is divided into variable-sized blocks according to the program's needs. This dynamic allocation helps reduce wastage of memory, leading to decreased internal fragmentation.

Advantages of Fragmentation

Below are the advantages of Fragmentation:

  • Efficient Memory Utilization: Fragmentation allows for the efficient use of memory by allocating smaller memory blocks that match the exact size of data, reducing wasted space
     
  • Improved Allocation Speed: Allocating smaller memory fragments can be faster than allocating large, contiguous blocks, especially in scenarios with varying memory demands
     
  • Flexibility: Fragmentation allows for more flexible memory allocation, accommodating data structures with different sizes and lifetimes
     
  • Reduced External Fragmentation: In the case of dynamic memory allocation, proper management of fragmentation can reduce the likelihood of external fragmentation, where memory is allocated but cannot be used effectively

Disadvantages of Fragmentation

Below are the disadvantages of Fragmentation:

  • Wasted Space: Can result in unused memory within allocated blocks which is internal fragmentation
     
  • Complex Management: Requires advanced algorithms for effective memory management
     
  • Overhead: Adds overhead in terms of time and memory used for management
     
  • Risk of Memory Exhaustion: Poor management can lead to "out of memory" errors despite available free memory

Frequently Asked Questions

What is fragmentation in operating system?

Fragmentation in operating systems is a condition in which memory is allocated but not used efficiently. This can happen for a variety of reasons, but the most common are internal fragmentation and external fragmentation.

What are the 4 types of fragmentation?

Fragmentation is a condition in which memory or storage space is allocated but not used efficiently. The four main types of fragmentation are internal fragmentation, external fragmentation, file fragmentation, and network fragmentation.

What is internal and external fragmentation?

Internal fragmentation occurs when allocated memory or disk space is larger than what is required by a process or file, wasting resources. External fragmentation arises when free memory or disk space is fragmented into smaller non-contiguous blocks.

How to avoid fragmentation in OS?

Fragmentation in the operating system can be minimized through strategies like memory compaction, dynamic memory allocation techniques (e.g., buddy system), and periodic disk defragmentation. Efficient memory and disk management practices help reduce both internal and external fragmentation.

What is the difference between fragmentation and segmentation?

Fragmentation refers to the division of memory or disk space into smaller, non-contiguous segments over time, impacting system performance. Segmentation is a memory management scheme that divides the memory into variable-sized segments to accommodate processes, each having its own logical address space.

Conclusion

In this article, we have discussed Fragmentation in OS. Fragmentation poses significant challenges to the efficiency and performance of operating systems. Whether in memory or disk storage, fragmentation can lead to wasted resources, increased access times, and degraded system performance.

Recommended Reading:

1. Introduction to Operatig System

2. Types of Operating System

3. Internal vs Extenral Fragmentation

4. Open Source Operating System
5. Components of Operating System

6. File management in operating system

7. mv command in linux

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