Fragmentation is a phenomenon in computer memory management where memory is divided into smaller sections that are not contiguous, which can cause wastage of memory and degradation of system performance.
There are two types of fragmentation:
External Fragmentation: External fragmentation occurs when free memory becomes scattered throughout the memory space, and there are no contiguous blocks of free memory that are large enough to satisfy an allocation request. This can occur when the memory is divided into fixed-sized blocks, and when blocks are allocated and deallocated over time, small gaps or holes are left between them. These gaps can add up to a significant amount of memory that cannot be used for any allocation requests, resulting in wastage of memory.
Internal Fragmentation: Internal fragmentation occurs when memory is allocated in fixed-sized blocks, and the size of the allocated block is greater than the size of the requested memory. The unused portion of the allocated memory block is wasted and cannot be used for any other allocations, resulting in memory wastage.
There are several methods to reduce fragmentation:
Compaction: This involves shifting allocated memory blocks so that free memory is contiguous and available in one large block. This technique is commonly used in operating systems to reduce external fragmentation.
Dynamic Memory Allocation: This technique involves allocating memory only as needed and returning it to the system when no longer needed. This reduces internal fragmentation by allocating exactly the amount of memory required.
Memory Pooling: This technique involves pre-allocating a large block of memory and dividing it into smaller fixed-sized blocks. This reduces external fragmentation by ensuring that all allocations are of the same size.
Segmentation: This technique involves dividing memory into segments of varying sizes, and each segment is allocated to a specific process or application. This technique reduces internal fragmentation by allowing for variable-sized allocations, but it can also result in external fragmentation if segments are not properly managed.