Last Updated on March 10, 2023 by Prepbytes
Contiguous memory allocation is a memory management technique used by operating systems to allocate a block of contiguous memory to a process. The allocation of contiguous memory to a process involves dividing the available memory into fixed-sized partitions or segments. The operating system then assigns one of these segments to a process when it is created.
What is Contiguous Memory Allocation in OS?
Contiguous memory allocation in os is a memory allocation process in which each process is allocated a contiguous block of memory, meaning that the memory locations for a process are consecutive.
Contiguous memory allocation is one of these memory allocation strategies. We use this technique to allocate contiguous blocks of memory to each process, as the name suggests. Therefore, we allot a continuous segment from the entirely empty space to the process based on its size whenever a process requests to enter the main memory.
Types of the Contiguous Memory Allocation Techniques
There are mainly two contiguous memory allocation techniques, which can be used to allocate the contiguous memory.
- Fixed-size partition schema
- Variable-size partition schema
1. Fixed-size Partition Schema:
Fixed-size partition schema is a technique used in contiguous memory allocation to divide the available memory into fixed-sized partitions or segments. Each partition is of a fixed size and can be allocated to a single process. The size of the partition is typically determined by the operating system and may be based on factors such as the amount of physical memory available and the expected size of the processes.
In this technique, each process gets the same amount of memory size thus this technique is also called static partition schema.
In the above example, we can see that the operating system has the same size partitions of 10 MB each and we have three processes having three different sizes 6 Mb, 2 Mb, and 8 Mb. Process 1 will be assigned to the first partition of 10 MB and process 1 will acquire whole partition of 10 MB. Similarly, Process 2 and Process 3 will acquire partitions two and three respectively. Both processes, Process 2 and Process 3 will acquire an entire partition of size 10 MB.
Advantages of the Fixed-size Partition Schema:
- Simplicity: Fixed-size partition schema is a simple technique for memory allocation. It is easy to implement, and the operating system can easily allocate and manage memory using this technique.
- Predictable behavior: Fixed-size partition schema is predictable since the size of the partition is fixed. The operating system can easily determine how much memory is available and can allocate it accordingly.
- Easy to manage: Fixed-size partition schema is easy to manage since the operating system can keep track of the start and end addresses of each allocated partition. This makes it easy to free up memory when a process terminates.
- Efficient allocation: Fixed-size partition schema is an efficient technique for memory allocation. The operating system can quickly search for a free partition of the appropriate size and allocate it to the process. This reduces the overhead involved in memory allocation.
Disadvantages of the Fixed-size Partition Schema:
- Limited flexibility: Fixed-size partition schema is inflexible since the size of each partition is fixed. This can be a disadvantage in systems with varying memory requirements or processes of different sizes. Processes that require more memory than the size of a partition cannot be accommodated using this technique.
- Internal fragmentation: One major disadvantage of the fixed-size partition schema is internal fragmentation. This occurs when a process does not use all of the memory allocated to it, resulting in unused memory in the partition. Over time, this unused memory can accumulate, reducing the overall efficiency of the memory management system.
- Unequal partition sizes: The fixed-size partition schema may lead to unequal partition sizes if the size of the memory is not divisible by the size of the partition. This can lead to inefficiencies in memory utilization since some partitions may remain unused.
2. Variable-size Partition Schema:
Variable-size partition schema is a technique used in contiguous memory allocation where the available memory is divided into partitions of varying sizes. Unlike fixed-size partition schema, the size of each partition is not fixed and can vary depending on the memory requirements of the processes.
In the above example, we can see that the operating system has the same size partitions of 10 MB each and we have three processes having three different sizes 6 Mb, 2 Mb, and 8 Mb. Now here, Process 1 only will be allocated only 6 MB not the entire partition of 10 MB. Similarly, Process 2 and Process 3 will be allocated 2 MB and 8 MB simultaneously.
Advantages of the Variable-size Partition Schema:
- Efficient memory utilization: The variable-size partition schema allows for efficient use of memory since the operating system can allocate memory blocks that are just the right size for each process, reducing the wastage of memory. This helps maximize the amount of available memory and increases the overall efficiency of the system.
- Flexibility: The variable-size partition schema is more flexible than the fixed-size partition schema since it can accommodate processes of different sizes. This makes it well-suited for systems with varying memory requirements.
- Reduced internal fragmentation: The variable-size partition schema can reduce internal fragmentation since the operating system can allocate only the required amount of memory for each process. This reduces the amount of unused memory in the system and can improve overall performance.
Disadvantages of the Fixed-size Partition Schema:
- External fragmentation: One major disadvantage of the variable-size partition schema is external fragmentation. External fragmentation occurs when there are small gaps between memory blocks, making it difficult to allocate memory for larger processes. Over time, these gaps can accumulate, reducing the overall efficiency of the memory management system.
- Increased complexity: The variable-size partition schema can be more complex to manage than the fixed-size partition schema. The operating system must keep track of the start and end addresses of each allocated memory block, making it more difficult to free up memory when a process terminates.
- Higher overhead: The variable-size partition schema requires additional overhead compared to the fixed-size partition schema. This is because the operating system must maintain a list or table of available memory blocks and their status, which can be time-consuming and resource-intensive.
Conclusion
In conclusion, this article will help you to understand what is continuous memory allocation in os. In addition, you will also learn types of contiguous memory allocation techniques along with the advantages and disadvantages of particular continuous memory allocation techniques.
Contiguous Memory Allocation – FAQs
1. How does contiguous memory allocation differ from non-contiguous memory allocation?
Contiguous memory allocation differs from non-contiguous memory allocation in that contiguous memory allocation allocates memory blocks that are located next to each other in memory, while non-contiguous memory allocation can allocate memory blocks that are located anywhere in memory.
2. What are the advantages of contiguous memory allocation?
The advantages of contiguous memory allocation include improved memory utilization, reduced overhead, and increased performance compared to non-contiguous memory allocation.
3. What are the disadvantages of contiguous memory allocation?
The disadvantages of contiguous memory allocation include the potential for fragmentation, the risk of memory leaks, and limitations in the amount of available memory that can be allocated.
4. Can contiguous memory allocation lead to memory fragmentation over time?
Yes, contiguous memory allocation can lead to memory fragmentation over time. Internal fragmentation can occur when a memory block is allocated to a process but the block is larger than the process needs. External fragmentation can occur when there are small gaps between allocated memory blocks that cannot be used to allocate memory for a larger process.
5. How does the operating system determine which memory block to allocate to a process?
The operating system determines which memory block to allocate to a process based on the memory management scheme being used. In fixed-size partition schema, the operating system assigns the first available partition that is large enough for the process. In variable-size partition schema, the operating system assigns a partition that is just the right size for the process.