Hello Friends! Today, we are going to cover all possible things about what is non contiguous memory allocation in OS and their exampleswith ease. This is unique article over the Internet. So, we can hope that at the end of this post; you will definitely fully aware about Non Contiguous Memory Allocation in Operating System without getting any obstacle.
What is Non Contiguous Memory Allocation?
Non-contiguous memory allocation in operating system involves allocating separate blocks of memory to a process that are not necessarily adjacent to each other. This technique is helpful when a process requires variable amounts of memory that are not contiguous. It is commonly implemented using pointers to link the non-contiguous memory blocks allocated to a process.
While non-contiguous allocation reduces internal fragmentation and allows for more flexible memory allocation. It can also lead to external fragmentation and slower memory allocation and deallocation times due to the use of pointers. This technique is used in many types of operating system such as Unix and Linux.
Virtual memory uses non-contiguous memory allocation to map non-contiguous physical memory to contiguous logical memory for each running process. This allows for more efficient use of physical memory and enables the system to handle larger programs and multiple processes simultaneously.
Article Hot Headlines:
In this section, we will show you all headlines about this entire article; you can check them as your choice; below shown all:
What is Non Contiguous Memory Allocation?
Types of Non Contiguous Memory Allocation
Applications of Non-Contiguous Memory Allocation
Advantages of Non-Contiguous Memory Allocation
Disadvantages of Non Contiguous Memory Allocation
FAQs (Frequently Asked Questions)
Why is Non-Contiguous Memory Allocation used in Operating Systems?
How does Paging work in Non-Contiguous Memory Allocation?
How does operating system manage fragmentation in Non-Contiguous Memory Allocation?
Let’s Get Started!!
Types of Non Contiguous Memory Allocation
Different kinds of Techniques are going to use for non-contiguous allocation in operating system, including:
Paging
Paging is a memory management technique that is used by operating systems to manage the virtual memory of computer system. In paging, the physical memory is divided into fixed-size blocks called frames, and the logical memory is divided into pages of the same size. The operating system maps pages to frames, allowing for efficient and flexible memory allocation.
Advantages of Paging
Easy Memory Management: Paging simplifies memory management, as the operating system only needs to keep track of the pages currently in memory rather than the entire address space.
Efficient Memory Usage: Paging allows for efficient memory usage by allocating memory in small, fixed-size blocks.
Eliminates External Fragmentation: Paging eliminates external fragmentation, as the data (page frames) can be scattered all over the physical memory.
Swapping: Paging supports efficient swapping between equal-sized pages and page frames, making it easy to swap out a page least likely to be used.
Virtual Memory Support: Paging enables virtual memory support, allowing each process to have its own address space, even if the physical memory is not large enough to accommodate all the processes.
Disadvantages of Paging
Internal Fragmentation: Since pages are of fixed size, there is a possibility for internal fragmentation, where the last page of a process is not fully used, leading to wasted memory.
Page Table Overhead: Paging requires page tables, which consume significant memory. Multilevel page tables and variable page sizes (super-pages) can mitigate this issue.
Complex Page Replacement: Paging can lead to complex page replacement algorithms, which can slow down the system.
Additional Layer of Memory Access:Paging introduces an additional layer of memory access, which can lead to longer memory access times.
Thrashing: Having too many pages in a physical memory at the same time can lead to thrashing, where the system spends more time swapping pages in and out of memory than executing instructions.
Multilevel Paging
Multilevel paging is an extension of the traditional paging scheme in operating systems; whereas the page table itself is structured hierarchically. Instead of having a single-level page table, the system uses a two-level or multi-level hierarchy of page tables.
Each level of the page table contains a subset of the virtual address space, and the page table entries point to the next level of the page table or to a physical memory frame. This is particularly useful when dealing with large address spaces and sparse address mappings.
Advantages of Multilevel Paging
Easy Memory Management: Multilevel paging simplifies memory management by dividing the address space into smaller, more manageable chunks.
Efficient Memory Usage: Multilevel paging allows for efficient memory usage by allocating memory in small, fixed-size blocks.
Faster Page Table Lookup: Multilevel paging can reduce the time required to perform a page table lookup, leading to faster system performance.
Flexibility: Multilevel paging provides greater flexibility in terms of how the memory space is organized, allowing the page table to be adjusted to accommodate changing needs.
Disadvantages of Multilevel Paging
Increased Complexity: Multilevel paging adds complexity to the memory management system, which can make it more difficult to design, implement, and debug.
Increased Overhead: Multilevel paging can increase the overhead associated with page table lookups, as each level must be traversed to find the desired page table entry.
Fragmentation: Multilevel paging can lead to fragmentation of the memory space, which can reduce overall system performance.
Inverted Paging
Inverted paging technique allows the operating system to map pages from primary virtual memory to a page in secondary storage memory, such as a hard disk. This technique enables faster context switching between tasks and reduces the number of I/O operations required.
Advantages of Inverted Paging
Faster Context Switching: Inverted paging enables faster context switching between tasks, which is crucial for efficient task execution.
Fewer I/O Operations: By mapping pages from primary virtual memory to a page in secondary storage, inverted paging reduces the number of I/O operations required, leading to faster task execution and better system performance.
Reduced Power Consumption: Since fewer I/O operations are required, power consumption is reduced.
Disadvantages of Inverted Paging
High Storage Cost: Inverted paging increases the storage cost of virtual memory, as it requires additional space to store the inverted page table.
Increased Page Table Size: Inverted paging increases the size of the page table, which can lead to slower page table lookups.
Increased Page Table Lookups: Inverted paging can result in an additional page table lookup, which may slow down the execution of the program.
Less Effective Page Replacement Algorithms: Inverted paging can cause page replacement algorithms to become less effective, as the page table structure is different from traditional paging.
Complexity: Inverted paging is more complex to implement than other paging techniques.
Segmentation
Segmentation is also a helpful memory management technique that is used in operating systems to divide a program into segments. Each segment represents a logical unit of the program, such as a procedure, function, or data structure. Then, every segment is assigned a unique identifier, and the segments can have variable sizes.
Process Isolation: It enhances process isolation, preventing one process from affecting others.
Sharing of Code & Data Segments: Segmentation facilitates the sharing of code and data segments among multiple processes.
Protection within Segments: Segmentation provides protection within segments and enhancing system security.
Disadvantages of Segmentation
Memory Fragmentation: Segmentation can lead to memory fragmentation; whereas available memory becomes inefficiently divided.
Complexity: It demands complex hardware and software support, contributing to system intricacy.
External Fragmentation: Segmentation can lead to external fragmentation, reducing memory efficiency.
Overhead: There is an overhead associated with keeping a segment table for each activity, which can impact system performance.
Security Risks: Security risks can emerge due to unauthorized segment access.
Segmented Paging
Segmented paging technique combines aspects of both segmentation and paging. It aims to leverage the benefits of segmentation, such as logical organization and protection. It also getting to address some of the challenges associated with fragmentation by incorporating paging.
Simplified Memory Allocations: It simplifies memory allocations, making it easier to manage memory for processes.
Improved Protection and Security: Segmented paging provides improved protection and security for processes, enhancing system security.
Disadvantages of Segmented Paging
External Fragmentation: Despite reducing external fragmentation, segmented paging can still lead to some level of external fragmentation, impacting memory efficiency.
Increased Hardware Resources: Segmented paging requires more hardware resources, which can lead to higher complexity and increased memory access time.
Page Table Size: The page table size is reduced as pages are present, reducing the memory requirements. Gives a programmers view along with the advantages of paging. It reduces external fragmentation in comparison with segmentation. Since the entire segment need not be swapped out.
Applications of Non-Contiguous Memory Allocation
Non-contiguous memory allocation is often used in various applications and scenarios, including:
Some Examples Are:
Virtual Memory Systems: Modern operating systems often use non-contiguous memory allocation for virtual memory systems. Virtual memory allows processes to use more memory than physically available by swapping data between RAM and disk storage. Memory pages can be scattered across different locations in RAM and secondary storage.
Heap Memory Management: Dynamic memory allocation in programming languages, such as C and C++, often involves non-contiguous memory allocation. The memory allocated using functions like malloc() or new may not be contiguous. As memory is allocated and deallocated dynamically, free memory blocks might be scattered throughout the heap.
File Systems: File systems, especially in distributed or networked environments, may use non-contiguous memory allocation. Files can be stored in a fragmented manner on disk, with different parts of a file residing in different physical locations on the storage media.
Database Management Systems:Databases often use non-contiguous memory allocation for storing and managing data. Tables and indexes may be distributed across different storage locations, and the data pages may not be stored consecutively.
Graphics and Multimedia Applications: Graphics and multimedia applications often work with large datasets, such as images, videos, or 3D models. Non-contiguous memory allocation may be employed to efficiently manage these datasets, especially when the data is too large to fit into a single contiguous block of memory.
Fragmentation-Aware Allocators: Memory allocators designed to handle fragmentation, like buddy allocators or slab allocators, may utilize non-contiguous memory allocation. These allocators manage memory efficiently, dealing with both internal and external fragmentation.
Memory-Mapped Files: Memory-mapped files allow files to be mapped directly into the virtual memory space of a process. These mappings may not be contiguous, and different portions of a file may be mapped to different regions of the process’s memory.
Network Packet Buffers: In networking applications, buffers used for storing network packets may be allocated in a non-contiguous manner. This allows for more flexible management of incoming and outgoing data streams.
Advantages of Non-Contiguous Memory Allocation
Non-contiguous memory allocation offers several advantages in various computing scenarios. Here are some of the key benefits of non-contiguous memory allocation, including:
Efficient Memory Utilization: It enables the system to allocate memory in smaller, scattered chunks rather than requiring a single, large contiguous block. This is particularly beneficial in scenarios where the memory needs of a process are dynamic and may not be known in advance.
Dynamic Memory Management: In applications where memory requirements change during runtime, non-contiguous allocation provides flexibility. Memory can be allocated and deallocated dynamically, and the freed memory can be reused for other purposes. This adaptability is crucial in environments with varying workloads.
Effective Handling of Fragmentation: Non-contiguous allocation can help mitigate the impact of memory fragmentation. Both external and internal fragmentation can be managed more effectively by allowing memory to be allocated in smaller pieces, reducing the likelihood of large unused gaps in memory.
Support for Virtual Memory Systems: Non-contiguous memory allocation is essential for the implementation of virtual memory systems. Virtual memory allows processes to use more memory than physically available by swapping data between RAM and disk storage. Non-contiguous allocation facilitates the paging mechanism, where pages of memory can be scattered across different locations.
Enhanced File System Efficiency: In file systems, non-contiguous memory allocation allows files to be stored in a fragmented manner on storage media. This can improve the efficiency of disk space utilization, especially when dealing with varying file sizes and frequent modifications.
Improved Heap Memory Management: Dynamic memory allocation in programming languages benefits from non-contiguous allocation, especially in scenarios where memory is allocated and deallocated frequently. Memory can be allocated in smaller chunks, leading to better heap utilization.
Adaptability to Large Datasets: Applications dealing with large datasets, such as graphics, multimedia, and databases, can benefit from non-contiguous memory allocation. It also enables the efficient management of enlarge amounts of data that may not suitable into a single contiguous block of memory.
Support for Memory-Mapped Files: Non-contiguous memory allocation is integral to memory-mapped files, allowing different portions of a file to be mapped into different regions of a process’s virtual memory space. This enables efficient and direct interaction with files as if they were portions of the process’s memory.
Disadvantages of Non Contiguous Memory Allocation
The disadvantages of non-contiguous memory allocation include:
Internal Fragmentation:It can lead to internal fragmentation, as memory is allocated in small, non-contiguous blocks, which may result in wasted memory within these blocks.
Slower Access: Access to memory can be slower than contiguous memory allocation, as it may require additional steps to access non-contiguous blocks, leading to slower memory access.
Increased Overhead: Non-contiguous allocation can increase overhead due to the use of pointers to link memory blocks, which can slow down memory allocation and deallocation processes.
External Fragmentation:It can also lead to external fragmentation, where the available memory is broken into small, non-contiguous blocks, making it difficult to allocate large blocks of memory to a process.
FAQs (Frequently Asked Questions)
Why is Non-Contiguous Memory Allocation used in Operating Systems?
Non-contiguous memory allocation is used to overcome the limitations of contiguous allocation, especially when dealing with fragmented memory. It is also helping out into efficiently utilizing available memory by getting to allocate portions of memory where they fit.
How does Paging work in Non-Contiguous Memory Allocation?
In paging, memory is divided into fixed-size blocks called pages. Processes are also divided into fixed-size blocks called page frames. The operating system swaps these pages between the primary memory and secondary storage. Paging helps in decreasing the fragmentation and offers the more flexible memory allocation approach.
How does operating system manage fragmentation in Non-Contiguous Memory Allocation?
Operating systems implement the several techniques to keep managing the fragmentation, such as compaction that is involved the shifting processes in memory to make contiguous free space, and memory allocation algorithms; its aims to minimize fragmentation. Paging and segmentation, if implemented wisely, can also help in mitigating fragmentation issues.
Summing Up
Through this article, you have been completely aware about what is non contiguous memory allocation in OS and their examples with ease. If this content is fruitful for you, then please share it along with your friends, family members or relatives over social media platforms like as Facebook, Instagram, Linked In, Twitter, and more.
