Memory Management Requirements
Memory management requirement is important to operating systems. The memory management function is to manage the computer’s primary memory storage. Since all new computers and laptops run multiple programs at any one time, it is imperative to manage what programs can run in the main memory or RAM and which programs can be swapped to secondary memory storage. Using memory management techniques and virtual memory systems process can efficiently manage an operating system. The quality of these techniques or systems can have an extensive effect on the overall system performance of the operating system.
Memory management methods such as single allocation, partitioned allocation, paged memory management, and segmented memory management are processes that are used to determine how memory is distributed through different processes. This process decides which program gets a space of the main memory, when the program can get the space, and how much memory space is available for each program. Single contiguous allocation is the easiest memory management method. The entire computer’s memory, except for the operating systems reserved memory, is available to a single application. Any operating system that uses single contiguous allocation can still multi-task by swapping the contents of memory to switch among applications. A partitioned allocation splits the main memory into multiple main memory partitions. In addition, each partition may contain information for a certain individual jobs or tasks. This memory management method consists of assigning a partition to a job when it starts and reassigning it when the job is complete. Paged memory management splits the computer’s main memory into fixed-sized units called page frames and the programs address space into pages of the size. With page memory management, each segment runs in its own address space. A process is loaded by loading all of its pages into available frames. Lastly, segmented memory management is a memory management technique that has a variable length block of data that is located in secondary memory. Each process is divided into a number of segments and the process is loaded by loading all of the segments into noncontiguous partitions. Segmentation allows better access protection than other structures because memory management process cannot access the data area of another process (Stallings, 1998).
Virtual memory system is a system where addressable memory extends beyond main storage using secondary storage managed by the system software in a way that programs can treat all of the designated storage as addressable main storage. The applications operate memory via virtual addresses. Each time an attempt to access stored data is made; virtual memory data orders translate the virtual address to a physical address. To completely implement virtual memory support, the system software needs to maintain a page table per task. The goal is to capture the virtual to physical page translation information for the entire address space (Zhou & Petrov, 2011). The traditional virtual memory system was designed decades ago to support the magnetic disk as the secondary storage. Recently, flash memory became a popular storage alternative for many portable devices with the continuing enhancements on its capacity, reliability and lower power utilization than mechanical hard drives (Tseng, Li, & Yang, 2006).
Memory management can be named as one of the most important parts of any operating system. Memory management techniques including virtual memory systems allows the operating system to maintain as many processors as possible in the main memory while swapping any processors that are not being used to the secondary memory. In today’s computer systems, the multi-core platforms are already becoming relevant because of how rapidly technology is moving. Anagnostopoulus et al. (2013) said, “Efficient use of memory utilization is a key challenge for application developers or programmers to achieve better memory management.”