Os Process Management Questions Medium
In operating systems, there are several memory allocation techniques used to manage the allocation and deallocation of memory for processes. These techniques include:
1. Contiguous Memory Allocation: This technique divides the main memory into fixed-sized partitions and assigns each partition to a process. It can be further classified into two types:
- Fixed Partitioning: In this technique, the memory is divided into fixed-sized partitions, and each partition is assigned to a process. It suffers from internal fragmentation as the allocated partition may be larger than the actual memory requirement of the process.
- Variable Partitioning: Here, the memory is divided into variable-sized partitions based on the process's memory requirement. It reduces internal fragmentation but may lead to external fragmentation.
2. Paging: Paging is a memory allocation technique that divides the physical memory into fixed-sized blocks called pages and the logical memory into fixed-sized blocks called frames. The pages of a process are loaded into available frames, and the mapping between pages and frames is maintained in a page table. Paging eliminates external fragmentation but may suffer from internal fragmentation.
3. Segmentation: Segmentation divides the logical memory into variable-sized segments, where each segment represents a logical unit of a program. Each segment is assigned to a process based on its memory requirements. It allows dynamic memory allocation but can lead to external fragmentation.
4. Virtual Memory: Virtual memory is a technique that allows processes to use more memory than physically available. It uses a combination of paging and demand paging to transfer pages between main memory and secondary storage (usually disk). It provides the illusion of a large memory space to processes and allows efficient memory management.
5. Buddy System: The buddy system is a memory allocation technique that divides the memory into fixed-sized blocks and allocates memory in powers of two. When a process requests memory, the system searches for the smallest available block that can satisfy the request. If the block is larger than required, it is split into two buddies. It helps in reducing external fragmentation but may suffer from internal fragmentation.
These memory allocation techniques are used by operating systems to efficiently manage the allocation and deallocation of memory for processes, ensuring optimal utilization of available resources.