Os Memory Management Questions Long
Memory fragmentation refers to the phenomenon where memory is divided into small, non-contiguous blocks, leading to inefficient utilization of memory resources. There are primarily two types of memory fragmentation: external fragmentation and internal fragmentation.
1. External Fragmentation:
External fragmentation occurs when free memory blocks are scattered throughout the system, making it difficult to allocate contiguous blocks of memory to satisfy larger memory requests. It arises due to the allocation and deallocation of variable-sized memory blocks over time. As a result, even if the total amount of free memory is sufficient to fulfill a request, it may not be possible to allocate a contiguous block, leading to wastage of memory.
External fragmentation can be further classified into two subtypes:
a) Contiguous External Fragmentation:
Contiguous external fragmentation occurs when free memory blocks are scattered randomly throughout the memory space. This fragmentation can be visualized as a series of small gaps between allocated memory blocks, making it challenging to allocate large contiguous blocks of memory.
b) Non-Contiguous External Fragmentation:
Non-contiguous external fragmentation occurs when free memory blocks are scattered in a non-contiguous manner, resulting in small, isolated free blocks. This type of fragmentation can occur when memory is allocated and deallocated in a non-linear fashion, leaving behind small gaps that cannot be utilized efficiently.
2. Internal Fragmentation:
Internal fragmentation occurs when allocated memory blocks contain unused memory within them. It arises due to the allocation of fixed-sized memory blocks, where the allocated block may be larger than the actual memory requirement of the process. The unused memory within the allocated block is wasted and cannot be utilized by other processes.
Internal fragmentation can be observed in scenarios such as fixed partitioning or when memory is allocated in fixed-sized pages. For example, if a process requires 10KB of memory but is allocated a fixed block of 16KB, there will be 6KB of unused memory within the allocated block, resulting in internal fragmentation.
To mitigate the impact of memory fragmentation, various memory management techniques are employed, such as compaction, paging, segmentation, and virtual memory. These techniques aim to optimize memory allocation and reduce fragmentation, ensuring efficient utilization of memory resources.