What Is Virtual Memory Simple Definition

Sometimes a user will see a message that the virtual memory is low, which means that more RAM needs to be added or the paging file size needs to be increased. Processor performance is affected by the number of cores, clock speed, and memory. There are different types of volatile and non-volatile memory. The process of translating virtual addresses to real addresses is called mapping. Copying virtual pages from disk to primary memory is called paging or swapping. Modern microprocessors for general purpose, a memory management unit or MMU, are integrated into the hardware. The task of the MMU is to translate virtual addresses into physical addresses. A basic example is given below – virtual memory was developed at a time when physical memory – also known as RAM – was expensive. Computers have a finite amount of RAM, so memory is eventually depleted when multiple programs are running at the same time. A system that uses virtual memory uses a section of the hard disk to emulate RAM.

With virtual memory, a system can load larger programs or several running programs at the same time, allowing each program to run as if it had more storage space without having to buy more RAM. In those early days, programmers used a process called overlay to run programs larger than the available memory. Parts of a program that were not used all the time were configured as overlays that replaced the existing overlay in memory if necessary. This required extensive programming to perform overlay work, which was a major impetus for the development of automated virtual memory. Segmentation is also used to manage virtual memory. This approach divides virtual memory into segments of different lengths. Segments that are not used in memory can be moved to the virtual memory area of the hard disk. Segmented information or processes are tracked in a segment table that indicates whether a segment exists in memory, whether it has changed, and what its physical address is. In addition, segmented file systems consist only of segments mapped to the potential address space of a process. The ability to run a program that is only partially in memory would thwart many advantages.

Page tables are used to translate the virtual addresses displayed by the application into physical addresses used by the hardware to process instructions. [20] This hardware that handles this particular translation is often referred to as the memory management unit. Each entry in the page table contains an indicator that indicates whether the corresponding page is in real memory or not. If it is in real memory, the page table entry contains the actual memory address where the page is stored. If the hardware references a page and the page table entry indicates that it is not currently in real memory, the appliance throws a page error exception that calls the paging supervisor component of the operating system. The main advantages of virtual memory include the freeing of applications from shared space management, the ability to share memory used by libraries between processes, increased security due to memory isolation, and the ability to conceptually use more memory than might be physically available, using the paging or segmentation technique. Less I/O would be required to load or replace each user program in memory. The main visible advantage of this scheme is that programs can be larger than physical memory. Virtual memory serves two purposes. First of all, it allows us to expand the use of physical memory by using hard drives. Secondly, it allows us to have memory protection because each virtual address is translated into a physical address. Virtual memory uses both hardware and software to allow a computer to compensate for physical memory constraints and temporarily transfer data from memory (RAM) to disk space.

By allocating blocks of memory to disk files, a computer can treat secondary storage as if it were primary memory. To make it easier to copy virtual memory to real memory, the operating system divides virtual memory into pages, each containing a fixed number of addresses. Each page is stored on a hard drive until it is needed. When the page is needed, the operating system copies it from disk to primary memory and translates virtual addresses into real addresses. Virtual memory is a type of memory management, a new trend in the technology used in computers. On the hardware (the physical part of the computer, e.B. CPU or graphics card) software is running. This software needs computer memory to run and do what it needs to do. Most computers used today can do more than one thing at a time, they run more than one application.

This is called multiprocessing. Other methods of replacing pages include FIFO (First-In-First-Out), Optimal Algorithm, and LRU (Least Recently Used) Page Replacement. With the FIFO method, memory selects the replacement of a page that has been in the virtual address for the longest time. The optimal algorithm method selects page replacements based on the page that is unlikely to be replaced after the longest period of time. While this is difficult to implement, it results in fewer page errors. The LRU page replacement method replaces the page that has not been used in memory for the longest time. Some computer systems, such as.B. embedded systems do not use virtual memory because they require a very fast response time or that always remains the same.

One of the problems is that with virtual memory, it is difficult to predict the response time. An application that uses a portion of memory that needs to be loaded from the hard drive has a different response time than one that does not. Therefore, the concept of virtual memory is not used in embedded systems. While there are advantages to using virtual memory, it also comes with some trade-offs that are worth considering, such as: Since your computer has a finite amount of RAM, it`s possible that memory will run out if too many programs run at the same time. This is where virtual memory comes in. Virtual memory increases your computer`s available memory by increasing the “address space” or storing the memory where data can be stored. To do this, disk space is used for the allocation of additional space. .

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