Linked List Allocation

A dynamic memory allocation method used in computer programming is called linked list allocation. In this method, a linked list data structure is used to distribute memory.

Memory is divided into a number of blocks of similar size when allocating a linked list. In the linked list, each block is symbolized by a node. A pointer to the following piece of memory is present at each node in the linked list. The final node in the linked list has a null pointer that serves as a marker for the list's conclusion.

Linked list data structure and its implementation in memory allocation

A linked list is a type of data structure that consists of a set of bumps, each of which has a reference to the following knot in the chain and some data. The list's last knot has a pointer that's set to null, signifying the list's end, and the first knot is known as the head. Memory allocation constantly makes use of the linked list data structure to keep track of the accessible memory blocks.

Memory is divided into a number of equal-sized blocks in Linked List Allocation, each of which is represented by a knot in the linked list. Every knot has a pointer to the following knot in the list and a data field with the position of the memory block.

Memory can be allocated and released in an effective manner using the linked list data structure. The allocator looks for a block of the requested size in the linked list when a program demands memory. A block with the requested size is allocated to the program if one is identified. If the requested size of the block is not accessible, the allocator may ask the operating system for more memory and add it to the linked list.

The allocator updates the pointers in the linked list to keep the order of available blocks whenever a block of memory is deallocated, marking the node that represents the block as available in the process. To lessen fragmentation, the allocator may combine neighboring free blocks of memory.

Allocation strategies in Linked List Allocation

In Linked List Allocation, the allocator searches the linked list for a memory block of the desired size according to the allocation strategies. In Linked List distribution, there are three typical distribution methods −

First-fit − In this tactic, the memory allocator begins its look at the head of the linked list and allocates the first memory block that is big enough to accommodate the request. The memory may become fragmented, but this is the simplest and fastest allocation method.

Best-fit − In this approach, the allocator looks through the complete linked list in search of the smallest memory block that is sizable enough to accommodate the request. While fragmentation is reduced, the additional searching that must be done could slow down allocation periods.

Worst-fit − Using this tactic, the allocator looks through the complete linked list for the biggest memory block that satisfies the request. While this may lead to bigger unused memory blocks and more fragmentation, it can be advantageous when large memory blocks are required.

Fragmentation of memory and techniques to reduce fragmentation in Linked List Allocation −

It becomes challenging to assign bigger, contiguous memory blocks when there are scattered small blocks of unused memory throughout the allotted memory space. Fragmentation can lessen the effectiveness of memory use and raise the risk of memory wear-out.

In Linked List Allocation, there are several methods to lessen splitting, such as −

Memory compaction − In this method, the allocated memory blocks are all moved to one end of the memory area, and the remaining empty space is then made available. To accomplish this, copy the information from the allocated blocks to a new location, and then update the linked list pointers to represent the new locations. Memory compression can take a while, and it might be necessary to pause the program while it's happening.

Coalescing adjacent free blocks − This method combines nearby free memory blocks to make bigger blocks. When a memory block is released, the allocator can determine whether the nearby blocks are also empty and combine them into a single, larger block if they are. This may lessen fragmentation and improve the accessibility of bigger memory regions.

Utilizing allocation techniques that reduce fragmentation − As was already mentioned, various allocation techniques can have various impacts on fragmentation. For instance, by choosing the smallest block of memory that can handle the requested size, best-fit allocation reduces fragmentation. Worst-fit allocation, on the other hand, tends to leave bigger free blocks of memory, which may result in more fragmentation.

Using memory pools − Memory pools are pre-allocated memory blocks that we break into smaller fixed-size pieces. This removes the requirement for random memory allocation and deallocation reduces the need for fragmentation. Software or users can easily request a memory block of the right size from the memory pool and then put it back into the pool when it is no longer required.

Advantages of Linked List allocation

In terms of memory management, Linked List Allocation has several benefits, including −

Flexibility − Linked List Allocation is a flexible option for dynamic memory allocation because it provides efficient memory allocation and deallocation.

Efficiency − Linked List Allocation allows for the efficient allocation and deallocation of memory by reducing fragmentation and maximizing memory utilization.

Scalability − Linked List Allocation is scalable for programs with changing memory usage patterns because it can manage varying memory requirements.

Disadvantages of Linked List allocation

Additionally, Linked List Allocation has some drawbacks, such as −

Memory overhead − Linked List Allocation can result in higher memory overhead because it needs extra memory to store the linked list.

Time complexity − When compared to other memory allocation strategies, Linked List Allocation may take longer to allocate and deallocate memory.

Fragmentation − Poor allocation and deallocation practices can result in fragmentation, which lowers the effectiveness of memory utilization.


Linked List allocation is a straightforward and dependable method that is easy to use in many programming languages. In this article, we discovered that this algorithm has benefits like scalability and flexibility. However, it also has drawbacks like slower time complexity and possible fragmentation. The decision to use Linked List Allocation should be based on the particular requirements of the program and the characteristics of the memory usage pattern.

Updated on: 03-May-2023

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