Home | Projects | Notes > Operating Systems > Summary of Memory Management Techniques
| Technique | Description | Strengths | Weaknesses |
|---|---|---|---|
| Fixed Partitioning | Main memory is divided into a number of static partitions as a system generation time. A process may be loaded into a partition of equal or greater size. | Simple to implement; little OS overhead. | Inefficient use of memory due to internal fragmentation; maximum number of active processes is fixed. |
| Dynamic Partitioning | Partitions are created dynamically, so each process is loaded into a partition of exactly the same size as that process. | No internal fragmentation; more efficient use of main memory. | Inefficient use of processor due to the need for compaction to counter external fragmentation. |
| Simple Paging | Main memory is divided into a number of equal size frames. Each process is divided into a number of equal-size pages of the same length as frames. A process is loaded by loading all of its pages into available, not necessarily contiguous, frames. | No external fragmentation. | A small amount of internal fragmentation. |
| Simple Segmentation | Each process is divided into a number of segments. A process is loaded by loading all of its segments into dynamic partitions that need not be contiguous. | No internal fragmentation; improved memory utilization and reduced overhead compared to dynamic partitioning. | External fragmentation. |
| Virtual Memory Paging | As with simple paging, except that it is not necessary to load all of the pages of a process. Nonresident pages that are needed are automatically brought in later. | No external fragmentation; higher degree of multiprogramming; large virtual address space. | Overhead of complex memory management. |
| Virtual Memory Segmentation | As with simple segmentation, except that it is not necessary to load all of the segments of a process. Nonresident segments that are needed are automatically brought in later. | No internal fragmentation, higher degree of multiprogramming; large virtual address space; protection and sharing support. | Overhead of complex memory management. |
Stallings, W. (2018). Operating Systems: Internals and Design Principles (9th ed.). Pearson Education, Inc.