Difference Between Internal Fragmentation and External Fragmentation
Main difference
The main difference between internal fragmentation and external fragmentation is that internal fragmentation is the storage space that remains unused between allocated memory blocks while external fragmentation is the holes between contiguous blocks that are too small to serve. an application.
Internal Fragmentation vs. External Fragmentation
Internal fragmentation is a type of fragmentation that occurs when a larger memory is allocated to a program rather than required. Here free space is known as internal fragmentation. On the other hand, external fragmentation is the type of free space that forms between non-contagious memory blocks.
The reason for internal fragmentation is partitioning of memory into blocks of fixed size. On the other hand, external fragmentation is the process that takes place when memory is divided into blocks of variable size depending on the size of different processes.
The problem of internal fragmentation can be solved by allocating memory to programs in dynamic portions of memory blocks as they wish and freeing it up when it is not needed during the execution of a program. On the other hand, external fragmentation can be resolved by paging, compaction, and segmentation so that memory can be allocated to a program in a non-contiguous manner.
Comparison chart
| internal fragmentation | external fragmentation |
| The difference between the memory needed for a program and the memory allocated is known as internal fragmentation. | Gaps or unused space that arises between non-contagious storage debris or fragments and is too short to store a new program is known as external fragmentation. |
| Refers to | |
| It refers to the space that remains unused between blocks in an allocated region. | It refers to the space that is left unused because it is too short to store a request. |
| Reason | |
| The reason for internal fragmentation is partitioning of memory into blocks of fixed size. | External fragmentation occurs when memory or storage is made up of blocks of various sizes based on the size of different programs. |
| Idea | |
| Occurs when more space is allocated to a program than is required. | It occurs when a program is removed from memory leaving free space which causes external fragmentation. |
| Solution | |
| It can be worked around by allocating memory to programs in dynamic portions of memory blocks as you like and freeing it up when you don’t need it during a program’s execution. | It can be resolved by paging, compaction, and segmentation, so memory can be allocated to a program in a non-contiguous manner. |
What is internal fragmentation ?
Internal fragmentation is a type of fragmentation that occurs when a larger memory is allocated to a program rather than required. Occurs when memory is allocated to blocks of fixed size.
Whenever a program demands memory, the system allocates a block of fixed size. So, if the memory allocated to the program is greater than the memory requested, then the difference between the memory required for a program and the memory allocated for it is known as internal fragmentation. This space within the fixed-size block cannot be allocated to any program because it would not be enough to store a new program.
The internal fragmentation problem can be solved by dividing memory into blocks of variable size and allocating the best sized block to a program that requires memory. It will not totally solve the problem of internal fragmentation, however it will mitigate it to some extent.
Example
Below is an example of internal fragmentation. The memory space is divided into fixed-size blocks of 18,470 bytes. But, a program demands 18,460 bytes. The system will allocate it with a partitioned block of fixed size, that is, 18,470 bytes. As a result, 10 bytes out of 18,470 bytes will remain empty, which is the source of internal fragmentation.
What is external fragmentation ?
External fragmentation is the gaps or unused space that arises between non-contagious memory or storage fragments and is too short to store a new program. Occurs when there is an adequate amount of free space in a system’s storage memory to meet the memory demand of a program. But the demand of the program cannot be implemented or satisfied as the available memory of the system is in a non-adjacent manner or mode.
Either you are applying first fit memory allocation strategy or best fit memory allocation strategy, it will be the reason for external fragmentation. It occurs when a program is loaded and removed from memory leaving free space that creates holes. There are a lot of these holes in the memory space that cause external fragmentation.
The first-fit and best-fit memory allocation strategy can reduce the amount of external fragmentation, but it cannot completely eliminate it. Pagination, compaction, and segmentation can solve external fragmentation.
The compaction algorithm causes the entire memory content to be moved to one side and frees up a large block of memory. But it is an expensive procedure. A workaround to resolve this issue is to allow a process to obtain physical memory noncontiguously. This solution can be achieved using the pagination and segmentation processes.
Example
In a computer system, when a program requests space, blocks are allocated in the form of chunks. Suppose that to store information and data in a system, there is only one empty portion of memory. Now, there is a program that we want to store in memory. The program will be saved dynamically in memory, that is, randomly, wherever you feel comfortable or discover space. When the next program needs to be saved, it will be adjusted accordingly in the memory space. Now, we remove a program from the system. It will leave space or a hole in the memory. This hole or space cannot be used by the other storage, even if it is present alongside free memory and causes external fragmentation to form.
Key differences
- The difference between the memory required for a program and the memory allocated for it is known as internal fragmentation, while the gaps or unused space that arises between non-contagious memory fragments and is too short to store a new program is known as as external fragmentation.
- Internal fragmentation refers to the space that remains unused between blocks in an allocated region, on the other hand, external fragmentation refers to the space that remains unused because it is too short to store a request.
- The reason for internal fragmentation is partitioning of memory into blocks of fixed size. In contrast, external fragmentation occurs when memory or storage is composed or divided into blocks of variable size depending on the size of different programs.
- Internal fragmentation occurs when more space is allocated to a program than is required. On the other hand, external fragmentation occurs when a program is removed from a memory leaving free space on the system storage which causes external fragmentation.
- The problem of internal fragmentation can be solved by allocating memory to programs in dynamic portions of memory blocks as they wish and freeing it up when it is not needed during the execution of a program. On the other hand, external fragmentation can be resolved by paging, compaction, and segmentation so that memory can be allocated to a program in a non-contiguous manner.
Final Thought
The above discussion summarizes that internal fragmentation and external fragmentation are two processes in computer storage that lead to wasted storage space. Internal fragmentation occurs when more space is allocated to a program than is required, while external fragmentation occurs when a program is removed from memory leaving free space.