Ch8 Kai

Chapter 8: Memory Management Strategies

8.1 Background

• Programs must be loaded into memory from disk to run.

• Main Memory: Physical memory where active processes reside (RAM).

• Memory management optimizes allocation during computation.

• Protection ensures correct operation and prevents unauthorized access.

8.2 Swapping

• Temporarily moves processes out of memory to a backing store for efficient memory usage.

• Process contexts can exceed available physical memory.

• Major part of swap time involves transfer to/from backing store.

• Swap mechanisms should manage pending I/O effectively.

8.3 Contiguous Memory Allocation

• Memory split into partitions for operating system and user processes.

• Processes require contiguous memory allocation.

• Fixed partitions limit multiprogramming due to fixed size.

• Dynamic or variable partitioning improves efficiency but can lead to fragmentation.

8.4 Segmentation

• Non-contiguous partitioning method aligning with program logical structure.

• Segments correspond to logical units (e.g., functions, arrays).

• Requires hardware support to maintain segment tables for offsets.

8.5 Paging

• Divides physical memory into fixed-size blocks (frames) and logical memory into pages.

• Simplifies memory allocation while avoiding external fragmentation but may cause internal fragmentation due to variable usage.

• Uses page tables for mapping logical to physical addresses.

• Can lead to increased overhead but supports non-contiguous memory allocation.